Vernon played in the Football League and the Scottish Premiership for 16 years, notably with lengthy spells with Oldham Athletic, Blackpool and Aberdeen.

During Blackpool's promotion season in 2006–07, he struggled to nail down a starting place and was third-choice striker behind the prolific Andy Morrell and Keigan Parker.

Due to the signings of Alan Gow and Steve Kabba, he found himself pushed out of the team, rejoining Colchester United, this time on a permanent deal.

Following the victory against Hibernian, the Dons' hit a poor run of form losing all of their next nine games, which resulted in the sacking of manager Mark McGhee.

Vernon started the 2011–12 season as the first choice striker, playing initially alongside Darren Mackie, but forming a better partnership with Northern Ireland international Josh Magennis.

On 11 January 2012, Vernon sat next to teammate Andrew Considine as the pair signed extensions to their current contracts.

[10] In the 2014 Scottish League Cup Final, Vernon came on as an extra-time substitute and scored in the penalty shoot-out to help Aberdeen win their first trophy for 19 years.

[12] On 18 June 2014, Vernon returned to English football, joining Shrewsbury Town in League Two on a two-year contract.

[17] Vernon struggled to stay in the side,[18] however a half-time formation change in an away match at Carlisle United in February 2015 saw him recalled in an advanced midfield role.

[22] He was recalled to the first-team when he featured as a substitute in an FA Cup first-round tie against Gainsborough Trinity in November 2015, where he claimed an assist for James Collins 71st-minute goal in a 1−0 victory over the non-league side.

[25] On 30 July 2016, Vernon signed a two-year contract with newly promoted League Two side Grimsby Town on a free transfer.

[30] Vernon ended the 2018–19 season as joint third-top scorer in the Northern Premier League Division One East, with 21 goals.