| Abbreviation | Definition |
|---|---|
| OPLA | Offshore Pollution Liability Agreement |
| OPM | Organic Pest Management |
| OPP | Other Pesticide Programs |
| OPPP | Oil Pollution Prevention Plan |
| OPPT | Office of Pollution Prevention and Toxics |
| OPRA | Operator and Pollution Risk Appraisal |
| OPRL | On Pack Recycling Label |
| OQA | Objective Quality Evident |
| ORCA | Otonabee Region Conservation Authority |
| ORCCR | Oak Ridges Corridor Conservation Reserve |
| OREP | Ocean Resources and Ecosystems Program |
| ORIS | Occurrence Report Information System |
| ORMCP | Oak Ridges Moraine Conservation Plan |
| ORRF | Organic Resource Recovery Facility |
| ORWRP | Olentangy River Wetland Research Park |
| OS | Oil Spill |
| OSC | One-Stop Carbon |
| OSCE | Open Space Conservation Easement |
| OSEC | Occupational Safety and Environmental Compliance |
| OSES | Occupational Safety and Environmental Services |