Colbeck made his Bradford City debut in a Carling Cup defeat to Notts County on 25 August 2004 at Valley Parade in his only game that season.[

He broke into the team the following season making 11 appearances.

During 2006-07 he was a regular in the City team but the team were relegated and Colbeck was sent off during a vital game against Oldham Athletic.

He scored his first senior goal against Lincoln City more than three years after his debut.

On 24 October 2007 he went on a month-long loan to Darlington to take the place of injured Julian Joachim.

He scored in both his second and third games there before the loan was extended for a second month.

The loan deal was cut short when he returned to Bradford City in December 2007 after he had made six appearances for Darlington.

He immediately went back into the Bradford side and later added his second goal for the club in a 2-0 win over Accrington Stanley on New Year's Day.

On 29 March Colbeck returned to the Darlington Arena to play against his former team-mates and celebrated Bradford City's 3-1 victory scoring the Bantams' third goal of the game.