| Open Systems Technology | South Australia |
| OpenLearning Ltd | |
| Openmarkets Australia Ltd | New South Wales |
| Openmesh | New South Wales |
| OpenSolar Pty Ltd | New South Wales |
| OpenSpatial | New South Wales |
| Opthea | Victoria |
| Opticalfibre | Queensland |
| Optima Technology | Victoria |
| Optimation Software Engineering Pty Ltd | Victoria |
| Optimax | |
| Optimising Pty Ltd | Victoria |
| Optisol Business Solutions | Queensland |
| Oracle Australia | New South Wales |
| Oracle Digital | |
| OracleStudio Pty Ltd | Queensland |
| Orange Digital | Queensland |
| Orbital8 Pty Ltd | Victoria |
| Ordermentum | New South Wales |
| Organik.services | Victoria |
| Organise Internet | |
| Orient Capital Pty Ltd | New South Wales |
| Orion Satellite Systems Pty Ltd | Western Australia |
| Orite IT Solutions | New South Wales |
| Orro Pty Ltd | New South Wales |
| Ortabe Pty Ltd | New South Wales |
| Orthocell Ltd | Western Australia |
| OSHatWork | Western Australia |
| OSINT Combine | New South Wales |
| Our Community House | Victoria |
| Outcomex | New South Wales |
| Overflow Internet | Queensland |
| OvertheWire Pty Ltd | Queensland |
| Ozbiz PCLawyer | New South Wales |
| Ozdoc | Queensland |
| Ozehosts.com | Western Australia |
| OzeVision Pty Ltd | Australian Capital Territory |
| Ozgene Pty Ltd | Western Australia |
| OzGuide Internet & Computer Solutions | Victoria |
| OzHosting.com Pty Ltd | New South Wales |
| OzISP | Victoria |
| Oziti Web Design | Western Australia |
| Ozius Spatial | Western Australia |
| OzLocal Australia | |
| OZNET IT & Media Services | New South Wales |
| OZtell | New South Wales |
| Ozzietel International Pty Ltd | New South Wales |
| Pacific Commerce | New South Wales |
| Pacific Telecommunications | Victoria |
| PageUp | Victoria |