 Grier began officiating football at age 18 and started as a high school football official in 1965, later moved on to college football in 1972, and eventually the NFL in 1981.His career ended abruptly during the 2004 NFL season when he was forced to retire due to a leg injury suffered during a series of games.He was replaced by the back judge on his crew, Scott Green, who had previous experience as a referee in NFL Europe.