He returned to the Senate following a recount after Stephen Parry was disqualified during the parliamentary eligibility crisis.

[3] In his early years, Colbeck gained qualifications in Small Business Management; Technology (Building); and Carpentry and Joinery Trade and Proficiency.

[4] Colbeck was appointed Parliamentary Secretary to the Minister for Agriculture, Fisheries and Forestry in October 2004.

He was shifted to the role of Shadow Parliamentary Secretary for Agriculture, Fisheries and Forestry in September 2008.

He blamed factional opponent Eric Abetz for his failure to win a higher position on the ticket.

[7] He polled an unusually high below-the-line tally, attributed to a strong "personal vote", but nonetheless lost his seat.

[9] Colbeck is considered to belong to the moderate wing of the Tasmanian Liberals, and supported Malcolm Turnbull during the 2018 leadership spills; he was reportedly the only Tasmanian Liberal not to sign the petition calling for a second spill.

[4] Prior to the 2019 federal election he was preselected in first place on the Liberals' Senate ticket and was re-elected.