| Abbreviation | Definition |
|---|---|
| OEA | Office of the Employers' Advisory (for WCB) |
| OESC | Ontario Electrical Safety Code |
| OFC | Ontario Fire Code |
| OFCC | Ohio Facilities Construction Commission |
| OFI | Owner Furnished Improvements |
| OFL | Ontario Federation of Labour |
| OGCA | Ontario General Contractors Association |
| OGT | On Going Training |
| OH | Over Hang |
| OHBA | Ontario Home Builders' Association |
| OHSA | Occupational Health & Safety Act |
| OHT | Over Head Tank |
| OHTR | optimal Hankel Transform Reconstruction |
| OHW | Oil-fired Hot Water heater |
| OICC | Officer In Charge of Construction |
| OITAB | Ontario Industry Training & Adjustment Board |
| OJSPC | Ontario Joint Standard Practice Committee |
| OLRB | Ontario Labour Relations Board |
| OMC | Odhisa Mining Corporation |
| OPC | Ordinary Portland Cement |