| Abbreviation | Definition |
|---|---|
| OSBB | Oregon Small Business Boost |
| OSBC | Open Source Business Conference |
| OSCC | Ontario Student Classics Conference |
| OSCC | Oregon Students of Color Conference |
| OSDC | Open Source Developers' Conference |
| OSDI | Operating Systems Design and Implementation Symposium |
| OSEC | Oregon Solar Energy Conference |
| OSEC | Oregon Sports and Entertainment Conference |
| OSiM | Open Source In Mobile |
| OSRC | Offshore Structures Reliability Conference |
| OSTR | Ontario Summit Trail Races |
| OTC | Offshore Technology Conference |
| OTC | One Team Conference |
| OTP | Occupy The Populace |
| OTTC | OnBase Training and Technology Conference |
| OUBC | Out for Undergraduate Business Conference (est. 2004) |
| OVAC | Ohio Valley Athletic Conference |
| OVC | Open Video Conference |
| OVC | Oregon Veterinary Conference |
| OVSC | Ohio Valley Shakespeare Conference |