| 4144 | O'Riley's Mine |    | U.S. Gold Ltd. (Datasoft Inc.) [unkn] | 28.nov.2009 |
| 906 | Ocean Conqueror [Big Box 2] | | Beau-Jolly Ltd. [unkn] | 15.oct.2005 |
| 4949 | Ocean Conqueror | | Hewson Consultants Ltd. (Rack-it) [1988] | 06.jun.2010 |
| 671 | Octapolis | | English Software Company [1987] | 03.jun.2007 |
| 1300 | Octoplex | | Mastertronic Ltd. (Mastertronic Added Dimension) [1989] | 03.jun.2007 |
| 2469 | Odyssey | | K-Tel International Ltd. [1984] | 03.jun.2007 |
| 5036 | Office Mate | | Gemini Marketing Ltd. [unkn] | 08.sep.2007 |
| 549 | Official F A Cup Football, The | | Mastertronic Ltd. (Ricochet) [1988] | 13.oct.2007 |
| 5642 | Official FA Cup 87 Football, The | | Virgin Games Ltd. [unkn] | 03.jun.2008 |
| 1551 | Official FA Cup Football, The | | Virgin Games Ltd. [1986] | 28.jun.2008 |
| 1414 | Official Father Christmas, The | | Alternative Software (299 Range) [1989] | 18.may.2008 |
| 1935 | Oh No! | | Firebird (Silverbird) [1988] | 07.nov.2009 |
| 5262 | Oil's Well | | Aackosoft [unkn] | 03.feb.2008 |
| 1473 | Oink [4 Most Toppers] | | Alternative Software Ltd. [unkn] | 18.may.2008 |
| 450 | Oink! | | CRL [1987] | 27.sep.2005 |
| 4560 | Oink! | | Alternative Software (199 Range) [unkn] | 06.jul.2006 |
| 75 | Okinawa [Conflicts 2] |  | Personal Software Services [unkn] | 03.jun.2007 |
| 4464 | Okinawa | | Personal Software Services [unkn] | 03.jun.2006 |
| 3606 | Old Bones [Cassette 50] | | Cascade Games Ltd. [unkn] | 22.jun.2008 |
| 640 | Olli & Lissa 3 [QUATTRO Cartoon] | | CodeMasters Ltd. (Quattro) [unkn] | 18.may.2008 |
| 877 | Olli & Lissa 3 | | CodeMasters Ltd. [1989] | 15.nov.2009 |
| 1096 | Olli and Lissa | | Firebird (Silver 199 Range) [1987] | 27.nov.2009 |
| 2280 | Ollie and Lissa [Chart Busters] | | Beau-Jolly Ltd. [unkn] | 01.oct.2005 |
| 1340 | Ollie's Follies | | U.S. Gold (Americana) [unkn] | 05.sep.2005 |
| 2733 | Ollo (Missions I & II) | | Bug-Byte [unkn] | 02.oct.2005 |
| 1341 | Olympic Skier | | U.S. Gold (Americana) [unkn] | 05.sep.2005 |
| 2075 | Olympic Skier [Triple Decker 7] | | Alternative Software (199 Range) [unkn] | 25.sep.2005 |
| 4193 | Olympic Skier | | Mr. Chip Software [1984] | 03.jun.2007 |
| 1525 | Olympic Spectacular | | Alternative Software (199 Range) [unkn] | 26.sep.2009 |
| 5832 | Olympics 84 | | Storm Software [unkn] | 19.sep.2008 |
| 4082 | Omega Run | | CRL [1984] | 13.dec.2008 |
| 1088 | On Court Tennis | | Firebird (Silver 199 Range) [unkn] | 27.nov.2009 |
| 3331 | On Court Tennis | | Activision, Inc. [1984] | 15.oct.2005 |
| 1883 | On Cue | | Mastertronic Ltd. (Mastertronic Added Dimension) [1987] | 14.jul.2007 |
| 548 | On Field Football | | Firebird (Silver 199 Range) [unkn] | 27.nov.2009 |
| 2006 | On the Bench | | Cult [1990] | 19.nov.2006 |
| 2689 | On the Tiles | | Firebird [1987] | 28.nov.2009 |
| 277 | On-Court Tennis | | Activision, Inc. [unkn] | 03.jun.2007 |
| 732 | On-Field Football [Sporting Classics] |  | Activision, Inc. [unkn] | 16.apr.2009 |
| 3815 | On-Field Football | | Activision, Inc. [unkn] | 30.dec.2005 |
| 5757 | One Bite Too Deep | | Reelax Games [unkn] | 26.jul.2008 |
| 6115 | One Day Cricket | | Melbourne House Ltd. [unkn] | 21.jun.2009 |
| 1268 | One Man and His Droid | | Mastertronic Ltd. (199 Range) [1985] | 03.jun.2007 |
| 1951 | One on One | | Ariolasoft Ltd. [1983] | 03.jun.2007 |
| 4328 | One-on-One | | Ariolasoft Ltd. [unkn] | 03.sep.2007 |
| 2488 | Oops! | | Big Apple, The [1988] | 09.jun.2006 |
| 5797 | Open Sesame | | Sulis Software [unkn] | 25.aug.2008 |
| 4614 | Operation Anoria | | Pirate Software [1988] | 13.nov.2007 |
| 3680 | Operation Fireball | | Alternative Software Ltd. [1987] | 05.feb.2008 |
| 1702 | Operation Hanoi | | Players (Players Premier) [1990] | 03.oct.2009 |
| 1394 | Operation Hormuz | | Alternative Software Ltd. (Again Again) [unkn] | 08.sep.2005 |
| 1431 | Operation Hormuz | | Alternative Software Ltd. [unkn] | 03.oct.2009 |
| 5805 | Operation Hormuz | | Alternative Software Ltd. (Again Again) [unkn] | 06.sep.2008 |
| 5653 | Operation Swordfish | | British Software [unkn] | 04.jun.2008 |
| 1020 | Operation Thunderbolt | | Ocean (The Hit Squad) [1991] | 14.jul.2007 |
| 2205 | Operation Thunderbolt | | Ocean Software Ltd. [1989] | 03.jun.2007 |
| 3417 | Operation Whirlwind | | Ariolasoft Ltd. [unkn] | 16.oct.2005 |
| 125 | Operation Wolf | | Ocean Software Ltd. [1988] | 10.jun.2007 |
| 959 | Operation Wolf | | Ocean (The Hit Squad) [1990] | 24.jun.2008 |
| 2949 | Operation Wolf [Mega Mix] | | Ocean Software Ltd. [1989] | 03.jun.2007 |
| 3055 | Operation Wolf [Biz, The] | | Ocean Software Ltd. [1989] | 25.nov.2006 |
| 3233 | Operation Wolf [Battle Stations] | | Ocean Software Ltd. [1988] | 29.dec.2005 |
| 3761 | Oracle's Cave, The | | Dorcas Software [unkn] | 27.dec.2005 |
| 544 | Orbitron | | Mastertronic Ltd. (199 Range) [1984] | 19.jan.2008 |
| 3608 | Orbitter [Cassette 50] | | Cascade Games Ltd. [unkn] | 22.jun.2008 |
| 2343 | Orc Attack | | Creative Sparks (Sparklers) [1984] | 03.jun.2007 |
| 4318 | Orc Attack [Sparklers Special] | | Creative Sparks (Sparklers) [unkn] | 05.may.2006 |
| 5483 | Orc Attack | | Creative Sparks [unkn] | 15.mar.2008 |
| 5775 | Orc Attack | | Maynard International Ltd. (Top Ten) [unkn] | 06.aug.2008 |
| 6091 | Orc Attack | | Compulogical S.A. [unkn] | 30.apr.2009 |
| 908 | Orion [Big Box 2] | | Beau-Jolly Ltd. [unkn] | 15.oct.2005 |
| 1805 | Orion | | Hewson Consultants Ltd. (Rack-it) [1988] | 28.dec.2008 |
| 5875 | Orion Quest | | Argus Press Software [unkn] | 29.oct.2008 |
| 6361 | Orm and Cheep: Narrow Squeaks | | Macmillan Ltd. [unkn] | 22.mar.2010 |
| 4932 | Orm and Cheep: The Birthday Party | | Macmillan Ltd. [unkn] | 15.dec.2009 |
| 3523 | Orpheus in the Underworld | | Alpha-Omega Software [unkn] | 03.nov.2005 |
| 6416 | Orpheus in the Underworld | | Powerhouse Publishing Ltd. [unkn] | 13.may.2010 |
| 1915 | Osmium | | Powerhouse Publishing Ltd. [1988] | 22.oct.2006 |
| 4095 | Osprey! | | Bourne Educational Software Ltd. [unkn] | 18.mar.2006 |
| 327 | Othello [Golden Oldies] | | Prism Leisure Corporation [unkn] | 03.jun.2007 |
| 5399 | Othello [Big 100, The] | | Wicked Software Ltd. [unkn] | 08.mar.2008 |
| 6392 | Othello | | Stack Computer Services Ltd. [unkn] | 17.apr.2010 |
| 126 | Out of This World | | Ariolasoft Ltd. [1987] | 06.jan.2008 |
| 127 | Out Run | | U.S. Gold [1987] | 06.jan.2008 |
| 1229 | Out Run | | U.S. Gold (Kixx) [1990] | 03.jun.2007 |
| 3808 | Out Run [Giants] | | U.S. Gold [unkn] | 17.dec.2006 |
| 4683 | Out Run [Coin Op Hits] | | U.S. Gold [unkn] | 01.oct.2006 |
| 2135 | Out Run Europa | | U.S. Gold [1991] | 13.sep.2008 |
| 2600 | Out Run Europa [Outrun Europa & G-Loc] | | U.S. Gold [1991] | 01.oct.2005 |
| 617 | Outback | | Paramount Software [1984] | 25.nov.2009 |
| 1541 | Outlaw | | Players (Players Premier) [1990] | 03.jun.2007 |
| 382 | Outlaws | | Ultimate Play the Game [unkn] | 13.aug.2008 |
| 5244 | Outlaws | | Mastertronic Ltd. (Ricochet) [unkn] | 04.oct.2008 |
| 6385 | Outrun Europa | | U.S. Gold (Kixx) [unkn] | 17.apr.2010 |
| 5536 | Over The Net | | Genias Software [1991] | 01.apr.2008 |
| 740 | Overlander | | Elite Systems Ltd. [1988] | 20.jul.2010 |
| 1103 | Overlander | | Elite Systems Ltd. (Encore) [unkn] | 17.apr.2006 |
| 3791 | Overlander [Story So Far 2, The] | | Elite Systems Ltd. [unkn] | 29.dec.2005 |
| 6499 | Overlander | | MCM Software [unkn] | 17.aug.2010 |
| 3615 | Overtake [Cassette 50] | | Cascade Games Ltd. [unkn] | 22.jun.2008 |
| 5330 | Oxxonian | | Topshots [unkn] | 18.feb.2008 |