O'Brien made his first grade debut in the 1984 season against South Sydney and played on the wing in Canterbury's 6-4 victory over Parramatta in the 1984 grand final. O'Brien was not a part of Canterbury's 1985premiership winning team but played in the 1986 4-2 loss to Parramatta in a tryless grand final. In 1988, O'Brien played in two finals games for Canterbury but was not included in the victorious grand final side which defeated Balmain. In 1989, O'Brien joined Balmain and played in the 1989 grand final against the Canberra Raiders which is regarded as one of the bestgrand finals of all time. O'Brien retired at the end of the 1992 season.