Brett Oliver joined Canterbury in 2000 as a halfback.

In 2001, Brett became a regular member of the Flegg team and played in the Premiership winning team against Cronulla from the bench.

In 2002, Brett became a regular member of the Premier League team and played in the Premiership winning team against St George Illawarra. 

In 2003, Brett was a regular member of the Premier League team before making his debut against Melbourne when Corey Hughes and Adam Perry were injured. Oliver scored on debut before returning to Premier League to play in the Preliminary Final against Penrith.

In 2004, Brett was a regular member of the Premier League team and played in the Qualifying Semi-Final against the Roosters.

In 2005, Brett's season was ruined by injury and in 2006, Brett joined Western Suburbs to play in the Premier League.