He made his first-team debut on 3 January 2004, coming on as a second-half substitute in a 2–0 FA Cup victory against Notts County.

He marked the occasion by scoring his first goal for the club, a last-minute equaliser that secured a 1–1 draw in the second leg and a 4–1 aggregate victory.

[citation needed] On 7 August 2007, Morrison signed a four-year contract with West Bromwich Albion, for an initial £1.5 million fee.

[10] Morrison made his Albion debut as a second-half substitute in a 2–1 defeat away at Burnley on the opening day of the 2007–08 season.

[17] On 30 June 2016, Morrison signed a new two-year deal with West Brom keeping him at the club until at least the summer of 2018 with a one-year option.

Along with Leicester City's Steve Howard and Aston Villa's Gabriel Agbonlahor, Morrison was one of a number of English Premier League players identified in June 2007 as being eligible to play for Scotland.

[citation needed] After retiring as a player in October 2019, Morrison started working as a coach in the West Bromwich Albion academy.

[22] He was promoted to a first-team coaching role in December 2020, following the appointment of Sam Allardyce as West Brom manager.

[32] Morrison joined the Scotland coaching staff during the June 2023 international break, replacing Steven Naismith.