| Objective Force: Commander | Xbox | Action | Cancelled |
| Obscure | Xbox | Survival/Horror | 3/29/2005 |
| Oddworld: Munch's Oddysee | Xbox | Adventure | 11/6/2001 |
| Oddworld: Stranger's Wrath | Xbox | Action/Shooter | 1/25/2005 |
| Open Season | Xbox | Action/Adventure | 9/19/2006 |
| Operation Flashpoint: Elite | Xbox | First Person Shooter | 11/8/2005 |
| Operation Flashpoint: Red River | Xbox | Action/Shooter | 6/7/2011 |
| Orchid | Xbox | Action | To Be Announced |
| Otogi 2: Immortal Warriors | Xbox | Action | 10/19/2004 |
| Otogi: Hyakki Toubatsu Emaki | Xbox | Action | To Be Announced |
| Otogi: Myth of Demons | Xbox | Action | 8/26/2003 |
| Otomedius Excellent | Xbox | Shooter | 7/19/2011 |
| Outlaw Golf | Xbox | Sports | 6/11/2002 |
| Outlaw Golf 2 | Xbox | Sports | 10/19/2004 |
| Outlaw Tennis | Xbox | Sports | 7/26/2005 |
| Outlaw Volleyball | Xbox | Sports | 7/8/2003 |
| OutRun 2006: Coast to Coast | Xbox | Racing/Driving | 4/25/2006 |
| OutRun2 | Xbox | Racing/Driving | 10/25/2004 |
| Over The Hedge | Xbox | Action/Adventure | 5/9/2006 |