 With a rookie contract in the 2006–07 season, Forrest made his first-class cricket debut for New South Wales against Queensland on 1 March 2007.After solid performances in early Pura Cup games, outstanding results in the Cricket Australia Cup and consistency for Hawkesbury in Grade Cricket, Forrest received his first full contract for New South Wales ahead of the 2007–08 season.Forrest made his List A cricket debut against Western Australia on 12 October 2007

In November 2007, Forrest scored his first first-class century against Tasmania at the Sydney Cricket Ground, hitting 177 runs including 21 fours and two sixes.