By profession, Moffat was a civil engineer. However, he remained an active and influential coach and official in the sport of football. Moffat was a member of football's Rules Committee for most of his adult life and, in that capacity, helped shape the game during its formative years. In October 1883, while still a student at Princeton, he was one of two Princeton representatives on an informal, seven-member rules committee that adopted the game's first modern scoring system—2 points for a touchdown, 4 points for a goal after touchdown, and 5 points for a field goal.