| Abbreviation | Definition |
|---|---|
| OPMC | Olympic Peninsula Motorcycle Club |
| OPRC | Oak Park Runners Club |
| OPRC | Old Peoples Riding Club |
| OPRC | Old Pueblo Radio Club |
| OPRC | Olde Providence Racquet Club |
| OPWC | Old Pueblo Wine Club |
| ORCC | Oak Ridge Country Club |
| ORCC | Off Road Camping Club |
| ORIF | Order of Rotary International Fellowship |
| ORPC | Ocean River Paddling Club |
| ORPC | Oundle Rifle Pistol Club |
| OSBC | Ocean State Bird Club |
| OSCC | Otago Sports Car Club |
| OSFC | Oregon State Flying Club |
| OSFC | Otter Street Fishing Club |
| OSGC | Oshawa Skeet and Gun Club |
| OSRC | Oakton Swim and Racquet Club |
| OSSC | Ohio State Swim Club |
| OSSC | Old Scotch Soccer Club |
| OSSC | Orlando Sport and Social Club |