| No. | Player | School | Pos. | Years |
|---|---|---|---|---|
| 85 | Oats, Carleton | Florida A&M | DT | 1965-72 |
| 4 | O'Connell, Aidan | Purdue | QB | 2023-Present |
| 61 | Ogas, Dave | San Diego State | LB | 1968 |
| 74 | Oglesby, Paul | UCLA | T | 1960 |
| 49 | Olawale, Jamize | North Texas | RB | 2012-17 |
| 56 | Oliver, Chip | USC | LB | 1968-69 |
| 85 | O'Malley, Ryan | Pennsylvania | TE | 2016 |
| 78 | Omameh, Patrick | Michigan | G | 2020 |
| 46 | O’Neal, Oren | Arkansas State | RB | 2007-09 |
| 59 | Onwualu, James | Notre Dame | LB | 2020 |
| 48 | Onwuasor, Patrick | Portland State | LB | 2021 |
| 98 | Osborne, Chuck | Arizona | DT | 1998-99 |
| 81 | Osborne, Clancy | Arizona State | LB | 1963-64 |
| 93 | Orr, Leon | Florida | DT | 2015 |
| 70 | Osemele, Kelechi | Iowa State | G-T | 2016-18 |
| 35 | O’Steen, Dwayne | San Jose State | DB | 1980-81 |
| 34 | Otto, Gus | Missouri | LB | 1965-72 |
| 50, 00 | Otto, Jim | Miami (Fla.) | C | 1960-74 |
| 44 | Owens, Burgess | Miami (Fla.) | DB | 1980-82 |
