Cooper was selected to represent New South Wales for the inaugural Origin game in 1980.
In 1982, Cooper was given the equal-longest suspension in rugby league history after he ran in to join a brawl and left three Illawarra Steelers flattened during a match at Wollongong Showground. Chairman of the NSWRFL's judiciary, Jim Comans, when handing down a fifteen-month suspension to Cooper, said, "Acts such as these must be obliterated from the game, and I'll begin by obliterating you."
Cooper attempted to keep fit during his suspension by playing Australian Rules football but after only four games with North Sydney in 1984 he dislocated his shoulder and retired from football.
Cooper was named in the second-row when the Western Suburbs Magpies named their Team of the Eighties.