| OAA | No Prefix Assigned |
| OAB | BCBS of Massachusetts |
| OAC | Anthem BCBS of Ohio |
| OAD | BCBS of Western New York |
| OAE | Anthem BCBS of Ohio |
| OAF | Anthem BCBS of Virginia |
| OAG | Anthem BCBS of Colorado |
| OAH | Empire BCBS of New York |
| OAI | Blue Shield of California |
| OAJ | No Prefix Assigned |
| OAK | Independence Blue-Cross of Philadelphia and Southeastern Pennsylvania |
| OAL | Blue Shield of California |
| OAM | Highmark BCBS of Pennsylvania |
| OAN | Carefirst BCBS |
| OAO | No Prefix Assigned |
| OAP | Anthem BCBS of Kentucky |
| OAQ | Carefirst BCBS |
| OAR | Carefirst BCBS |
| OAS | Anthem BCBS of Indiana |
| OAT | BCBS of Nebraska |
| OAU | BCBS of Michigan |
| OAV | No Prefix Assigned |
| OAW | No Prefix Assigned |
| OAX | No Prefix Assigned |
| OAY | No Prefix Assigned |
| OAZ | BCBS of Massachusetts |
| OBA | Anthem Blue-Cross |
| OBB | Highmark BCBS of Pennsylvania |
| OBC | BCBS of Massachusetts |
| OBD | Florida-Blue |
| OBE | BCBS of Michigan |
| OBF | Highmark BCBS of Pennsylvania |
| OBG | No Prefix Assigned |
| OBH | No Prefix Assigned |
| OBI | BCBS of Minnesota |
| OBJ | Premera BCBS of Alaska |
| OBK | No Prefix Assigned |
| OBL | Carefirst BCBS |
| OBM | Carefirst BCBS |
| OBN | BCBS of Massachusetts |
| OBO | Highmark BCBS of Pennsylvania |
| OBP | Blue Shield of California |
| OBQ | Anthem Blue-Cross |
| OBR | Wellmark BCBS |
| OBS | No Prefix Assigned |
| OBT | BCBS of Arizona |
| OBU | BCBS of Alabama |
| OBV | Anthem BCBS of Georgia |
| OBW | Independence Blue-Cross of Philadelphia and Southeastern Pennsylvania |
| OBX | Anthem BCBS of Georgia |
| OBY | No Prefix Assigned |
| OBZ | No Prefix Assigned |
| OCA | Anthem Blue-Cross |
| OCB | No Prefix Assigned |
| OCC | No Prefix Assigned |
| OCD | Blue Shield of California |
| OCE | No Prefix Assigned |
| OCF | BCBS of Louisiana |
| OCG | Wellmark BCBS |
| OCH | BCBS of Western New York |
| OCI | Anthem BCBS of Wisconsin |
| OCJ | No Prefix Assigned |
| OCK | Florida-Blue |
| OCL | No Prefix Assigned |
| OCM | Wellmark BCBS |
| OCN | Regence BCBS |
| OCO | Blue Shield of California |
| OCP | Anthem BCBS of Ohio |
| OCQ | No Prefix Assigned |
| OCR | Independence Blue-Cross of Philadelphia and Southeastern Pennsylvania |
| OCS | No Prefix Assigned |
| OCT | Blue-Cross of Idaho |
| OCU | Anthem BCBS of Ohio |
| OCV | Carefirst BCBS |
| OCW | Anthem Blue-Cross |
| OCX | Carefirst BCBS |
| OCY | Carefirst BCBS |
| OCZ | Independence Blue-Cross of Philadelphia and Southeastern Pennsylvania |
| ODA | Carefirst BCBS |
| ODB | Anthem BCBS of Ohio |
| ODC | No Prefix Assigned |
| ODD | No Prefix Assigned |
| ODE | No Prefix Assigned |
| ODF | BCBS of Massachusetts |
| ODG | No Prefix Assigned |
| ODH | No Prefix Assigned |
| ODI | BCBS of Western New York |
| ODJ | BCBS of Tennessee |
| ODK | Carefirst BCBS |
| ODL | BCBS of Tennessee |
| ODM | BCBS of Arizona |
| ODN | BCBS of Tennessee |
| ODO | Carefirst BCBS |
| ODP | No Prefix Assigned |
| ODQ | Highmark BCBS of Pennsylvania |
| ODR | Carefirst BCBS |
| ODS | BCBS of Western New York |
| ODT | BCBS of Massachusetts |
| ODU | No Prefix Assigned |
| ODV | Wellmark BCBS |
| ODW | BCBS of Michigan |
| ODX | BCBS of Alabama |
| ODY | BCBS of Michigan |
| ODZ | BCBS of Michigan |
| OEA | Anthem BCBS of Virginia |
| OEB | Anthem BCBS of Virginia |
| OEC | No Prefix Assigned |
| OED | No Prefix Assigned |
| OEE | Florida-Blue |
| OEF | Carefirst BCBS |
| OEG | BCBS of Kansas City |
| OEH | Anthem Blue-Cross |
| OEI | BCBS of Nebraska |
| OEJ | Blue Shield of California |
| OEK | BCBS of Michigan |
| OEL | Carefirst BCBS |
| OEM | Anthem BCBS of Virginia |
| OEN | No Prefix Assigned |
| OEO | No Prefix Assigned |
| OEP | No Prefix Assigned |
| OEQ | BCBS of Michigan |
| OER | Regence BCBS |
| OES | Anthem Blue-Cross |
| OET | Carefirst BCBS |
| OEU | Highmark BCBS of Pennsylvania |
| OEV | Highmark Blue Shield of Pennsylvania |
| OEW | BCBS of North Dakota |
| OEX | No Prefix Assigned |
| OEY | BCBS of Michigan |
| OEZ | BCBS of South Carolina |
| OFA | Anthem BCBS of Indiana |
| OFB | Capital Blue-Cross of Pennsylvania |
| OFC | BCBS of Michigan |
| OFD | No Prefix Assigned |
| OFE | No Prefix Assigned |
| OFF | BCBS of Western New York |
| OFG | BCBS of Rhode Island |
| OFH | Anthem BCBS of Ohio |
| OFI | No Prefix Assigned |
| OFJ | BCBS of Michigan |
| OFK | No Prefix Assigned |
| OFL | Carefirst BCBS |
| OFM | Carefirst BCBS |
| OFN | BCBS of Tennessee |
| OFO | Anthem Blue-Cross |
| OFP | Anthem Blue-Cross |
| OFQ | BCBS of Michigan |
| OFR | No Prefix Assigned |
| OFS | BCBS of Western New York |
| OFT | Blue Shield of California |
| OFU | BCBS of Michigan |
| OFV | BCBS of Michigan |
| OFW | BCBS of Michigan |
| OFX | Anthem BCBS of Missouri |
| OFY | Blue Shield of California |
| OFZ | BCBS of Michigan |
| OGA | No Prefix Assigned |
| OGB | No Prefix Assigned |
| OGC | Wellmark BCBS |
| OGD | Anthem BCBS of Ohio |
| OGE | No Prefix Assigned |
| OGF | BCBS of Michigan |
| OGG | No Prefix Assigned |
| OGH | Anthem BCBS of Georgia |
| OGI | No Prefix Assigned |
| OGJ | BCBS of Michigan |
| OGK | BCBS of Michigan |
| OGL | Wellmark BCBS |
| OGM | Premera BCBS of Alaska |
| OGN | Anthem BCBS of Kentucky |
| OGO | BCBS of Michigan |
| OGP | No Prefix Assigned |
| OGQ | No Prefix Assigned |
| OGR | No Prefix Assigned |
| OGS | BCBS of Louisiana |
| OGT | BCBS of Western New York |
| OGU | Highmark BCBS of Pennsylvania |
| OGV | No Prefix Assigned |
| OGW | BCBS of Louisiana |
| OGX | Carefirst BCBS |
| OGY | No Prefix Assigned |
| OGZ | No Prefix Assigned |
| OHA | BCBS of South Carolina |
| OHB | Anthem BCBS of Ohio |
| OHC | BCBS of Michigan |
| OHD | BCBS of Texas |
| OHE | BCBS of Rhode Island |
| OHF | Anthem BCBS of Virginia |
| OHG | Anthem BCBS of Virginia |
| OHH | Anthem BCBS of Indiana |
| OHI | BCBS of Louisiana |
| OHJ | Anthem BCBS of Kentucky |
| OHK | Wellmark BCBS |
| OHL | Highmark BCBS of Pennsylvania |
| OHM | Blue Shield of Northeastern New York |
| OHN | Wellmark BCBS |
| OHO | Anthem BCBS of Ohio |
| OHP | Anthem BCBS of Ohio |
| OHQ | No Prefix Assigned |
| OHR | Anthem BCBS of Colorado |
| OHS | Anthem BCBS of Ohio |
| OHT | Anthem BCBS of Ohio |
| OHU | Wellmark BCBS |
| OHV | BCBS of Rhode Island |
| OHW | No Prefix Assigned |
| OHX | BCBS of Rhode Island |
| OHY | BCBS of Michigan |
| OHZ | BCBS of Rhode Island |
| OIA | No Prefix Assigned |
| OIB | Highmark BCBS of Pennsylvania |
| OIC | Independence Blue-Cross of Philadelphia and Southeastern Pennsylvania |
| OID | Blue-Cross of Idaho |
| OIE | No Prefix Assigned |
| OIF | No Prefix Assigned |
| OIG | Highmark BCBS of Pennsylvania |
| OIH | No Prefix Assigned |
| OII | BCBS of Michigan |
| OIJ | BCBS of Michigan |
| OIK | BCBS of Michigan |
| OIL | Highmark BCBS of Pennsylvania |
| OIM | Independence Blue-Cross of Philadelphia and Southeastern Pennsylvania |
| OIN | Highmark BCBS of Pennsylvania |
| OIO | BCBS of Michigan |
| OIP | Blue Shield of California |
| OIQ | BCBS of Michigan |
| OIR | Highmark BCBS of Pennsylvania |
| OIS | BCBS of Western New York |
| OIT | BCBS of Michigan |
| OIU | BCBS of Michigan |
| OIV | BCBS of Michigan |
| OIW | BCBS of Michigan |
| OIX | BCBS of Michigan |
| OIY | BCBS of Michigan |
| OIZ | Anthem Blue-Cross |
| OJA | No Prefix Assigned |
| OJB | No Prefix Assigned |
| OJC | No Prefix Assigned |
| OJD | No Prefix Assigned |
| OJE | BCBS of Michigan |
| OJF | BCBS of Michigan |
| OJG | No Prefix Assigned |
| OJH | No Prefix Assigned |
| OJI | BCBS of Michigan |
| OJJ | BCBS of Michigan |
| OJK | BCBS of Michigan |
| OJL | BCBS of Michigan |
| OJM | Anthem BCBS of Missouri |
| OJN | BCBS of Michigan |
| OJO | BCBS of Michigan |
| OJP | BCBS of Rhode Island |
| OJQ | BCBS of Michigan |
| OJR | Wellmark BCBS |
| OJS | No Prefix Assigned |
| OJT | Carefirst BCBS |
| OJU | No Prefix Assigned |
| OJV | BCBS of Michigan |
| OJW | Regence BCBS |
| OJX | BCBS of Michigan |
| OJY | BCBS of Michigan |
| OJZ | No Prefix Assigned |
| OKA | BCBS of Minnesota |
| OKB | Carefirst BCBS |
| OKC | BCBS of Oklahoma |
| OKD | Independence Blue-Cross of Philadelphia and Southeastern Pennsylvania |
| OKE | Carefirst BCBS |
| OKF | BCBS of Michigan |
| OKG | BCBS of Michigan |
| OKH | Anthem Blue-Cross |
| OKI | BCBS of Michigan |
| OKJ | BCBS of Michigan |
| OKK | BCBS of Michigan |
| OKL | Arkansas BCBS |
| OKM | Independence Blue-Cross of Philadelphia and Southeastern Pennsylvania |
| OKN | BCBS of Michigan |
| OKO | BCBS of Michigan |
| OKP | Independence Blue-Cross of Philadelphia and Southeastern Pennsylvania |
| OKQ | BCBS of Michigan |
| OKR | Anthem BCBS of Colorado |
| OKS | BCBS of Western New York |
| OKT | Anthem BCBS of Ohio |
| OKU | No Prefix Assigned |
| OKV | BCBS of Michigan |
| OKW | Anthem Blue-Cross |
| OKX | BCBS of Michigan |
| OKY | BCBS of Michigan |
| OKZ | BCBS of Michigan |
| OLA | BCBS of Kansas City |
| OLB | Wellmark BCBS |
| OLC | No Prefix Assigned |
| OLD | Blue Shield of California |
| OLE | No Prefix Assigned |
| OLF | No Prefix Assigned |
| OLG | Premera BCBS of Alaska |
| OLH | BCBS of Arizona |
| OLI | BCBS of Michigan |
| OLJ | No Prefix Assigned |
| OLK | No Prefix Assigned |
| OLL | No Prefix Assigned |
| OLM | Arkansas BCBS |
| OLN | BCBS of Alabama |
| OLO | No Prefix Assigned |
| OLP | No Prefix Assigned |
| OLQ | BCBS of Michigan |
| OLR | No Prefix Assigned |
| OLS | Carefirst BCBS |
| OLT | Wellmark BCBS |
| OLU | Anthem BCBS of Colorado |
| OLV | BCBS of Michigan |
| OLW | BCBS of Western New York |
| OLX | BCBS of Michigan |
| OLY | BCBS of Michigan |
| OLZ | BCBS of Michigan |
| OMA | Anthem BCBS of Ohio |
| OMB | Anthem BCBS of Ohio |
| OMC | No Prefix Assigned |
| OMD | Independence Blue-Cross of Philadelphia and Southeastern Pennsylvania |
| OME | Wellmark BCBS |
| OMF | No Prefix Assigned |
| OMG | BCBS of Michigan |
| OMH | Blue Shield of California |
| OMI | Anthem BCBS of Georgia |
| OMJ | No Prefix Assigned |
| OMK | Anthem BCBS of Missouri |
| OML | Florida-Blue |
| OMM | No Prefix Assigned |
| OMN | No Prefix Assigned |
| OMO | No Prefix Assigned |
| OMP | BCBS of Michigan |
| OMQ | BCBS of Massachusetts |
| OMR | BCBS of Rhode Island |
| OMS | BCBS of Massachusetts |
| OMT | BCBS of Michigan |
| OMU | No Prefix Assigned |
| OMV | Carefirst BCBS |
| OMW | No Prefix Assigned |
| OMX | Anthem BCBS of Colorado |
| OMY | No Prefix Assigned |
| OMZ | Blue Shield of California |
| ONA | Anthem BCBS of Missouri |
| ONB | Anthem BCBS of Ohio |
| ONC | Anthem BCBS of Indiana |
| OND | Wellmark BCBS |
| ONE | Anthem BCBS of Indiana |
| ONF | No Prefix Assigned |
| ONG | BCBS of Massachusetts |
| ONH | BCBS of Minnesota |
| ONI | Anthem BCBS of Indiana |
| ONJ | No Prefix Assigned |
| ONK | No Prefix Assigned |
| ONL | Anthem BCBS of Ohio |
| ONM | No Prefix Assigned |
| ONN | No Prefix Assigned |
| ONO | Blue Shield of California |
| ONP | Anthem BCBS of Missouri |
| ONQ | BCBS of Alabama |
| ONR | No Prefix Assigned |
| ONS | BCBS of Alabama |
| ONT | BCBS of Massachusetts |
| ONU | Carefirst BCBS |
| ONV | Carefirst BCBS |
| ONW | Anthem BCBS of Indiana |
| ONX | Anthem BCBS of Indiana |
| ONY | BCBS of Minnesota |
| ONZ | Anthem BCBS of Indiana |
| OOA | Blue Shield of California |
| OOB | Blue Shield of California |
| OOC | BCBS of Massachusetts |
| OOD | BCBS of Michigan |
| OOE | BCBS of Michigan |
| OOF | BCBS of Michigan |
| OOG | Blue Shield of California |
| OOH | Independence Blue-Cross of Philadelphia and Southeastern Pennsylvania |
| OOI | BCBS of Michigan |
| OOJ | BCBS of Michigan |
| OOK | BCBS of Michigan |
| OOL | BCBS of Rhode Island |
| OOM | Anthem Blue-Cross |
| OON | BCBS of Michigan |
| OOO | BCBS of Michigan |
| OOP | Blue Shield of California |
| OOQ | BCBS of Michigan |
| OOR | BCBS of North Carolina |
| OOS | Blue Shield of California |
| OOT | Blue Shield of California |
| OOU | BCBS of Michigan |
| OOV | BCBS of Michigan |
| OOW | BCBS of Michigan |
| OOX | BCBS of Michigan |
| OOY | No Prefix Assigned |
| OOZ | BCBS of Michigan |
| OPA | BCBS of Louisiana |
| OPB | Highmark BCBS of Pennsylvania |
| OPC | No Prefix Assigned |
| OPD | Anthem BCBS of Wisconsin |
| OPE | Anthem BCBS of Georgia |
| OPF | Anthem BCBS of Wisconsin |
| OPG | Anthem Blue-Cross |
| OPH | No Prefix Assigned |
| OPI | Blue-Cross of North Carolina |
| OPJ | Anthem BCBS of Wisconsin |
| OPK | Anthem BCBS of Wisconsin |
| OPL | No Prefix Assigned |
| OPM | No Prefix Assigned |
| OPN | No Prefix Assigned |
| OPO | No Prefix Assigned |
| OPP | Wellmark BCBS |
| OPQ | No Prefix Assigned |
| OPR | Wellmark BCBS |
| OPS | BCBS of Massachusetts |
| OPT | Carefirst BCBS |
| OPU | Anthem BCBS of Wisconsin |
| OPV | Anthem BCBS of Wisconsin |
| OPW | Anthem BCBS of Wisconsin |
| OPX | Anthem BCBS of Wisconsin |
| OPY | Independence Blue-Cross of Philadelphia and Southeastern Pennsylvania |
| OPZ | Anthem BCBS of Wisconsin |
| OQA | No Prefix Assigned |
| OQB | Anthem Blue-Cross |
| OQC | Independence Blue-Cross of Philadelphia and Southeastern Pennsylvania |
| OQD | BCBS of Michigan |
| OQE | BCBS of Michigan |
| OQF | BCBS of Michigan |
| OQG | BCBS of Michigan |
| OQH | BCBS of Michigan |
| OQI | BCBS of Michigan |
| OQJ | BCBS of Michigan |
| OQK | BCBS of Michigan |
| OQL | BCBS of Michigan |
| OQM | BCBS of Michigan |
| OQN | BCBS of Michigan |
| OQO | BCBS of Michigan |
| OQP | Anthem Blue-Cross |
| OQQ | BCBS of Michigan |
| OQR | BCBS of Michigan |
| OQS | Anthem Blue-Cross |
| OQT | BCBS of Michigan |
| OQU | BCBS of Michigan |
| OQV | BCBS of Michigan |
| OQW | BCBS of Michigan |
| OQX | No Prefix Assigned |
| OQY | No Prefix Assigned |
| OQZ | No Prefix Assigned |
| ORA | No Prefix Assigned |
| ORB | Wellmark BCBS |
| ORC | Anthem BCBS of Kentucky |
| ORD | Independence Blue-Cross of Philadelphia and Southeastern Pennsylvania |
| ORE | BCBS of Tennessee |
| ORF | BCBS of Michigan |
| ORG | BCBS of Tennessee |
| ORH | Anthem BCBS of Missouri |
| ORI | BCBS of South Carolina |
| ORJ | BCBS of Michigan |
| ORK | Anthem BCBS of Ohio |
| ORL | Anthem Blue-Cross |
| ORM | Blue Shield of Northeastern New York |
| ORN | Horizon BCBS of New Jersey |
| ORO | BCBS of Michigan |
| ORP | No Prefix Assigned |
| ORQ | BCBS of Michigan |
| ORR | No Prefix Assigned |
| ORS | Regence BCBS |
| ORT | Capital Blue-Cross of Pennsylvania |
| ORU | BCBS of Tennessee |
| ORV | BCBS of Michigan |
| ORW | No Prefix Assigned |
| ORX | Blue-Cross of Idaho |
| ORY | Blue Shield of California |
| ORZ | Horizon BCBS of New Jersey |
| OSA | No Prefix Assigned |
| OSB | BCBS of Alabama |
| OSC | No Prefix Assigned |
| OSD | No Prefix Assigned |
| OSE | BCBS of Arizona |
| OSF | No Prefix Assigned |
| OSG | No Prefix Assigned |
| OSH | Carefirst BCBS |
| OSI | Independence Blue-Cross of Philadelphia and Southeastern Pennsylvania |
| OSJ | Anthem BCBS of Ohio |
| OSK | No Prefix Assigned |
| OSL | BCBS of Nebraska |
| OSM | BCBS of Illinois |
| OSN | No Prefix Assigned |
| OSO | Independence Blue-Cross of Philadelphia and Southeastern Pennsylvania |
| OSP | No Prefix Assigned |
| OSQ | Highmark BCBS of Pennsylvania |
| OSR | Independence Blue-Cross of Philadelphia and Southeastern Pennsylvania |
| OSS | Blue Shield of California |
| OST | Highmark BCBS of Delaware |
| OSU | No Prefix Assigned |
| OSV | Independence Blue-Cross of Philadelphia and Southeastern Pennsylvania |
| OSW | Anthem BCBS of Ohio |
| OSX | Wellmark BCBS |
| OSY | BCBS of Kansas City |
| OSZ | Anthem BCBS of Virginia |
| OTA | Florida-Blue |
| OTB | Anthem BCBS of Virginia |
| OTC | BCBS of Nebraska |
| OTD | Anthem Blue-Cross |
| OTE | Anthem BCBS of Indiana |
| OTF | Anthem BCBS of Indiana |
| OTG | BCBS of Michigan |
| OTH | BCBS of Tennessee |
| OTI | BCBS of North Dakota |
| OTJ | Carefirst BCBS |
| OTK | Wellmark BCBS |
| OTL | BCBS of Alabama |
| OTM | Blue Shield of California |
| OTN | BCBS of North Dakota |
| OTO | No Prefix Assigned |
| OTP | Blue Shield of California |
| OTQ | Anthem BCBS of Connecticut |
| OTR | No Prefix Assigned |
| OTS | Independence Blue-Cross of Philadelphia and Southeastern Pennsylvania |
| OTT | Wellmark BCBS |
| OTU | Wellmark BCBS |
| OTV | No Prefix Assigned |
| OTW | Anthem BCBS of Georgia |
| OTX | Blue Shield of California |
| OTY | Regence BCBS |
| OTZ | Anthem BCBS of Ohio |
| OUA | Regence BCBS |
| OUB | BCBS of Rhode Island |
| OUC | BCBS of South Carolina |
| OUD | BCBS of Michigan |
| OUE | BCBS of Rhode Island |
| OUF | Regence BCBS |
| OUG | No Prefix Assigned |
| OUH | Empire BCBS of New York |
| OUI | Horizon BCBS of New Jersey |
| OUJ | BCBS of Michigan |
| OUK | BCBS of Michigan |
| OUL | BCBS of Michigan |
| OUM | BCBS of Michigan |
| OUN | BCBS of Michigan |
| OUO | BCBS of Michigan |
| OUP | Wellmark BCBS |
| OUQ | BCBS of Michigan |
| OUR | Horizon BCBS of New Jersey |
| OUS | No Prefix Assigned |
| OUT | Horizon BCBS of New Jersey |
| OUU | BCBS of Michigan |
| OUV | BCBS of Michigan |
| OUW | Highmark BCBS of West Virginia |
| OUX | BCBS of Michigan |
| OUY | BCBS of Michigan |
| OUZ | BCBS of Michigan |
| OVA | No Prefix Assigned |
| OVB | No Prefix Assigned |
| OVC | Independence Blue-Cross of Philadelphia and Southeastern Pennsylvania |
| OVD | BCBS of Michigan |
| OVE | No Prefix Assigned |
| OVF | No Prefix Assigned |
| OVG | BCBS of Michigan |
| OVH | Premera BCBS of Alaska |
| OVI | BCBS of Michigan |
| OVJ | No Prefix Assigned |
| OVK | No Prefix Assigned |
| OVL | BCBS of Western New York |
| OVM | Wellmark BCBS |
| OVN | BCBS of Michigan |
| OVO | BCBS of Michigan |
| OVP | Anthem BCBS of Indiana |
| OVQ | BCBS of Michigan |
| OVR | Carefirst BCBS |
| OVS | No Prefix Assigned |
| OVT | Anthem BCBS of Ohio |
| OVU | BCBS of Michigan |
| OVV | BCBS of Michigan |
| OVW | Highmark BCBS of West Virginia |
| OVX | BCBS of Michigan |
| OVY | BCBS of Michigan |
| OVZ | BCBS of Michigan |
| OWA | Wellmark BCBS |
| OWB | Carefirst BCBS |
| OWC | Regence BCBS |
| OWD | Carefirst BCBS |
| OWE | Florida-Blue |
| OWF | Wellmark BCBS |
| OWG | BCBS of Western New York |
| OWH | Anthem BCBS of Connecticut |
| OWI | Anthem BCBS of Ohio |
| OWJ | Anthem BCBS of Virginia |
| OWK | BCBS of Michigan |
| OWL | Blue Shield of California |
| OWM | No Prefix Assigned |
| OWN | No Prefix Assigned |
| OWO | BCBS of Michigan |
| OWP | No Prefix Assigned |
| OWQ | BCBS of Michigan |
| OWR | BCBS of Michigan |
| OWS | Anthem BCBS of Virginia |
| OWT | Anthem BCBS of Georgia |
| OWU | BCBS of Michigan |
| OWV | No Prefix Assigned |
| OWW | Anthem BCBS of Virginia |
| OWX | Anthem BCBS of Ohio |
| OWY | Anthem BCBS of Ohio |
| OWZ | Wellmark BCBS |
| OXA | BCBS of Western New York |
| OXB | No Prefix Assigned |
| OXC | No Prefix Assigned |
| OXD | Anthem Blue-Cross |
| OXE | BCBS of Michigan |
| OXF | No Prefix Assigned |
| OXG | BCBS of Michigan |
| OXH | BCBS of Michigan |
| OXI | BCBS of Michigan |
| OXJ | BCBS of Michigan |
| OXK | BCBS of Michigan |
| OXL | BCBS of Michigan |
| OXM | Premera BCBS of Alaska |
| OXN | Regence BCBS |
| OXO | BCBS of Western New York |
| OXP | Anthem Blue-Cross |
| OXQ | BCBS of Michigan |
| OXR | BCBS of Michigan |
| OXS | No Prefix Assigned |
| OXT | BCBS of Michigan |
| OXU | BCBS of Michigan |
| OXV | BCBS of Michigan |
| OXW | BCBS of Michigan |
| OXX | BCBS of Michigan |
| OXY | BCBS of Michigan |
| OXZ | No Prefix Assigned |
| OYA | Wellmark BCBS |
| OYB | Anthem Blue-Cross |
| OYC | Horizon BCBS of New Jersey |
| OYD | Blue-Cross of Idaho |
| OYE | No Prefix Assigned |
| OYF | BCBS of Michigan |
| OYG | BCBS of Michigan |
| OYH | Anthem BCBS of Ohio |
| OYI | BCBS of Michigan |
| OYJ | BCBS of Michigan |
| OYK | BCBS of Michigan |
| OYL | Blue Shield of California |
| OYM | Independence Blue-Cross of Philadelphia and Southeastern Pennsylvania |
| OYN | BCBS of Michigan |
| OYO | BCBS of Michigan |
| OYP | No Prefix Assigned |
| OYQ | BCBS of Michigan |
| OYR | BCBS of Michigan |
| OYS | Blue Shield of California |
| OYT | BCBS of Michigan |
| OYU | BCBS of Michigan |
| OYV | No Prefix Assigned |
| OYW | BCBS of Michigan |
| OYX | BCBS of Michigan |
| OYY | BCBS of Michigan |
| OYZ | No Prefix Assigned |
| OZA | Anthem BCBS of Missouri |
| OZB | Anthem BCBS of Wisconsin |
| OZC | Horizon BCBS of New Jersey |
| OZD | Anthem BCBS of Virginia |
| OZE | BCBS of Michigan |
| OZF | BCBS of Michigan |
| OZG | Blue Shield of California |
| OZH | No Prefix Assigned |
| OZI | BCBS of Michigan |
| OZJ | BCBS of Michigan |
| OZK | Anthem BCBS of Missouri |
| OZL | BCBS of Michigan |
| OZM | Anthem BCBS of Virginia |
| OZN | BCBS of Michigan |
| OZO | No Prefix Assigned |
| OZP | Anthem Blue-Cross |
| OZQ | BCBS of Michigan |
| OZR | BCBS of Michigan |
| OZS | BCBS of Western New York |
| OZT | BCBS of Michigan |
| OZU | BCBS of Michigan |
| OZV | BCBS of Michigan |
| OZW | No Prefix Assigned |
| OZX | Anthem BCBS of Missouri |
| OZY | BCBS of Michigan |
| OZZ | BCBS of Michigan |
| O2A | Blue Cross of California |
| O2E | Blue Cross of California |
| O2N | Highmark BCBS of Pennsylvania |
| O2T | Blue Cross Blue Shield of Minnesota |
| O3T | Regence Blue Cross Blue Shield of Oregon |
| O3V | Premera Blue Cross |
