| Oakland University (Rochester, Michigan) | The Men and Women Golden Grizzlies |
| Oberlin College (Oberlin, Ohio) | The Women Yeomen The Men Yeomen |
| Occidental College (Los Angeles) | The Women Tigers The Men Tigers |
| Ocean County College (Toms River, New Jersey) | The Men and Women Vikings |
| Ohio Northern University (Ada) | The Women Polar Bear The Men Polar Bear |
| The Ohio State University (Columbus) | The Women Buckeyes The Men Buckeyes |
| Ohio University (Athens) | The Women Bobcats |
| Ohio Wesleyan University (Delaware, Ohio) | The Women Battling Bishop The Men Battling Bishop |
| Oklahoma Baptist University (Shawnee) | The Women Bison The Men Bison |
| Old Dominion University (Norfolk, Virginia) | The Men and Women Monarchs |
| State University College at Old Westbury (Old Westbury, New York) | The Women Panthers The Men Panthers |
| Olivet College (Olivet, Michigan) | The Women Fighting Comets The Men Fighting Comets |
| Olivet Nazarene University (Bourbonnais, Illinois) | The Women Tiger The Men Tiger |
| State University College at Oneonta (Oneonta, New York) | The Women Red Dragons The Men Red Dragons |
| Oregon State University (Corvallis) | The Women Beaver |
| State University at Oswego (Oswego, New York) | The Women Lakers The Men Lakers |
| Ouachita Baptist University (Arkadelphia, Arkansas) | The Women Tiger Sharks The Men Tiger Sharks |