| Abbreviation | Definition |
|---|---|
| OIQ | Ordre des Ingénieurs du Québec |
| OIRCA | Ontario Industrial Roofing Contractors' Association |
| OIRSA | Organismo Internacional Regional de Sanidad Agropecuaria |
| OKA | Ontario Kinesiology Association |
| OKTA | Overseas Korean Traders Associations |
| OLBPA | Old Louisville Business and Professional Association |
| OLCA | Ohio Lawn Care Association |
| OLGA | Old Ladies Golf Association |
| OLS | Ontario Land Surveyor |
| OMCI | Ohio Metal Casting Industry |
| OMEA | Ociationontario Music Educators Association |
| OMEA | Ontario Music Educators Association |
| OMEA | Ontario Music Educators' Association |
| OMEP | Oregon Manufacturing Extension Partnership |
| OMFED | OSC (Orissa State Cooperative) Milk Producers' Federation Limited |
| OMIC | Ophthalmic Mutual Insurance Company |
| OMLA | Oregon Mortgage Lenders Association |
| OMM | Organizacion Mundial de Medicina Natural |
| OMMA | Ottawa Mixed Media Artists |
| OMU | Offshore Mariners United |