| OCA.P | O2 Capital Inc. | TSX Venture | Suspended |
| OGC | OceanaGold Corp. | TSX | Active |
| OCP | Ocean Park Ventures Corp | TSX Venture | Active |
| OCC.P | Oceanside Capital Corp | TSX Venture | Suspended |
| OCC | Oceanside Capital Corp | TSX Venture | Active |
| OCS.UN | OCP Credit Stgy Un | TSX | Active |
| OVX.H | Oculus Ventures Corporation | TSX Venture | Active |
| OVX.P | Oculus Ventures Corporation | TSX Venture | Delisted |
| ODS | Odesia Group Inc. | TSX Venture | Active |
| ODN | Odin Mining and Exploration Ltd. | TSX Venture | Active |
| ODE | Odyssey Petroleum Corp. | TSX Venture | Active |
| ODX | Odyssey Resources Limited | TSX Venture | Active |
| OIL.H | Oilexco Incorporated | TSX Venture | Suspended |
| OOI.P | Oil Optimization Inc | TSX Venture | Delisted |
| OOI.H | Oil Optimization Inc. | TSX Venture | Active |
| OSM.UN | Oil Sand MegaProj Un | TSX | Active |
| OCF.WT | OilSands Canada Corporation | TSX | Delisted |
| OCF | OilSands Cda Corp Eq | TSX | Active |
| OSF.UN | Oil Sands Sector Un | TSX | Active |
| OST.PR.A | Oil Sands Splt Tr Pr | TSX | Active |
| OST.UN | Oil Sands Splt Tr Un | TSX | Active |
| OCB.A | O'Leary Advantaged Tactical Global Corporate Bond Fund | TSX | Delisted |
| OCB.WT | O'Leary Adv Bond Wt | TSX | Active |
| OCB.UN | OLeary Advntg Bnd Un | TSX | Active |
| OBF.UN | O'Leary BrIC-Plus Un | TSX | Active |
| OBF.WT | O'Leary BrIC-Plus Wt | TSX | Active |
| OCZ.UN | O'Leary Cdn Eqty Un | TSX | Active |
| OCZ.WT | O'Leary Cdn Eqty Wt | TSX | Active |
| OCY.UN | O'Leary Cdn Incm Un | TSX | Active |
| OCY.WT | O'Leary Cdn Incm Wt | TSX | Active |
| OFS.UN | O'Leary Founder's Un | TSX | Active |
| OFS.WT | O'Leary Founder's Wt | TSX | Active |
| OGE.UN | O'Leary Glbl Eqty Un | TSX | Active |
| OGE.WT | O'Leary Glbl Eqty Wt | TSX | Active |
| OGO.UN | OLeary Incm Oppor Un | TSX | Delisted |
| OLV | Olivut Resources Ltd. | TSX Venture | Active |
| OLY | Olympia Financial Group Inc | TSX Venture | Active |
| OYM | Olympus Pacific Min | TSX | Active |
| OML | Omni-Lite Industries Canada Inc | TSX Venture | Active |
| OMT | OMT Inc. | TSX Venture | Active |
| ONC | Oncolytics Biotech | TSX | Active |
| OBP | Ondine Biopharma J | TSX | Active |
| OM | OneMove Technologies Inc | TSX Venture | Active |
| OWI | One World Investments Inc | TSX Venture | Active |
| OCX | Onex Corporation SV | TSX | Active |