1962 | 2–4 Players | Abstract Strategy | Board Games | Junior (8+) | Medium-Length Games (1 to 2 hours) | Starts with O Oh-Wah-Ree (1962)
1975 | 2 Players | Board Games | Medium-Length Games (1 to 2 hours) | Modern Warfare | Starts with O | Teen (12+) | Wargame Oil War: American Intervention in the Persian Gulf (1975)
1–2 Players | 1975 | Board Games | Short Games (30 minutes to 1 hour) | Starts with O | Teen (12+) | Wargame | World War II Okinawa: The Last Battle, April 1945 (1975)
1992 | 2 Players | Abstract Strategy | Board Games | Junior (8+) | Quick Games (Under 30 minutes) | Starts with O Omega Chess (1992)
1–4 Players | 1992 | Board Games | Deduction | Electronic | Exploration | Family | Long Games (Over 2 hours) | Older Teen (14+) | Science Fiction | Starts with T | Thematic The Omega Virus (1992)
1987 | 2 Players | Board Games | Quick Games (Under 30 minutes) | Starts with O | Teen (12+) | Wargame | World War II Onslaught (1987)
1 Players | 1988 | Adventure | Board Games | Short Games (30 minutes to 1 hour) | Starts with O | Teen (12+) | Wargame | World War II Open Fire: Solitaire Tank Combat in WWII (1988)
1–6 Players | 1965 | Action / Dexterity | Board Games | Children's Game | Medical | Primary Schooler (6+) | Short Games (30 minutes to 1 hour) | Starts with O Operation (1965)
1970 | 2 Players | Board Games | Expansion for Base-game | Quick Games (Under 30 minutes) | Starts with O | Teen (12+) | Wargame | World War II Operation ‘GREIF’ (1970)
1980 | 2 Players | Board Games | Civil War | Modern Warfare | Print & Play | Short Games (30 minutes to 1 hour) | Starts with O | Teen (12+) | Vietnam War | Wargame Operation Pegasus (1980)