Cousins played as a rover and stood at 175 centimetres in height. After playing in the WAFL between 1970 and 1974 for the Perth Football Club, he was recruited to the VFL to play with Geelong where he made his debut in 1975. He went on to play 67 games for the club until 1979 when he returned to Perth. Cousins continued to play WAFL football until 1987. Cousins tied on votes for the 1983 Sandover Medal, but was beaten on a countback by John Ironmonger; in 1997, the WAFL awarded him a retrospective Sandover Medal. In his two stints at Perth, Cousins played 240 games and kicked 309 goals. He also represented Western Australia in State of Origin football.
South Australia 30.18 (198) defeated Western Australia 16.15 (111), at Subiaco Oval, 15 June 1985
Victoria 19.16 (130) defeated Western Australia 9.11 (65), at Subiaco Oval, 16 July 1985