| Abbreviation | Definition |
|---|---|
| OATA | Ohio Agricultural Technologies Association |
| OATA | Ohio Athletic Trainers' Association |
| OATA | Ontario Air Transport Association |
| OATA | Oregon Automotive Trades Association |
| OATA | Ornamental Aquatic Trade Association, LTD. |
| OAW | Opticians Association of Washington |
| OBA | Oklahoma Bankers Association |
| OBA | Oklahoma Bar Association |
| OBA | Old Bostonian Association |
| OBA | One Bar Association |
| OBA | Ontario Bar Association |
| OBA | Ontario Beekeepers' Association |
| OBA | Oregon Bankers Association |
| OBA | Outdoor Basketball Association |
| OBC | Outrageous Builders Club |
| OBCE | Organized Board Civil Engineers |
| OBCMAI | Orange Blossom Country Music Association, Inc. |
| OBLPC | Oregon Board of Licensed Professional Counselors |
| OBO | Oregon Board of Optometry |
| OCA | Ohio Collectors Association |