All Members with last names starting with: o
| Oakley, George | Riverdale |
| O'Connor, Hamilton Parke | Bruce South |
| O'Connor, Lawrence | Durham--York |
| O'Connor, Terrance P. | Oakville |
| O'Donoghue, Daniel John | Ottawa |
| O'Donoghue, Daniel John | Ottawa |
| Offer, Steven | Mississauga North |
| O'Keefe, George O. | Ottawa (2 Seats) |
| Oke, Leslie Warner | Lambton East |
| Olde, Neil Leverne | Middlesex South |
| Oliver, Adam | Oxford South |
| Oliver, Adam | Oxford South |
| Oliver, Farquhar Robert | Grey South |
| O'Neil, Hugh Patrick | Quinte |
| O'Neill, John | Toronto Southeast -- Seat A |
| O'Neill, Yvonne | Ottawa--Rideau |
| Orazietti, David | Sault Ste. Marie |
| Ostrom, Gilbert Wellington | Hastings West |
| O'Sullivan, John C. | Peterborough East |
| O'Toole, John | Durham |
| Ouellette, Jerry J. | Oshawa |
| Overall, Cyril Arthur Goodwin | Niagara Falls |
| Owen, Bruce | Simcoe Centre |
| Owens, Edward William James | Toronto Southeast -- Seat B |
| Owens, Stephen David | Scarborough Centre |