After scoring 12 goals in 59 games for Norwich in the top tier of English football, Morison signed for Leeds United in January 2013.

Morison scored the winning goal in the 2017 EFL League One play-off final to help Millwall achieve promotion back into the Championship during the 2016–17 season.

[4] He impressed manager Kevan Broadhurst and subsequently made his debut at the end of the 2001–02 season in a 2–2 draw against Cambridge United.

[17] He started the 2006–07 season by scoring two goals in two games for Stortford,[18][19] before joining Conference National club Stevenage Borough on a two-year deal in August 2006 for a "small four figure fee".

[22] Morison scored regularly for Stevenage during his debut season, helping the club to success in the FA Trophy, finishing as the competition's top goalscorer with eight goals.

There was a clause in the contract that stated he could leave the club at the end of the 2008–09 season for a pre-arranged fee if Stevenage did not win promotion into the Football League.

[33] He missed the next three games through suspension, but returned in early September 2008, following up a hat-trick against eventual champions Burton Albion with a brace against Altrincham.

[36][37][38] Morison played regularly during the club's successful FA Trophy campaign in the 2008–09 season, scoring seven times in seven games, including a goal in the 2–0 victory against York in the final on 9 May 2009.

[54] Morison subsequently signed a new 2+1⁄2-year contract with Millwall on 5 February 2011, ending transfer speculation about his long-term commitment to the club.

[56] At the end of the 2010–11 season, Morison handed in a written transfer request amid speculation about a move to newly promoted Premier League club Norwich City.

[62] Morison made his Norwich City debut against Wigan Athletic during the club's first game of the 2011–12 season, playing 75 minutes of the match in a 1–1 draw.

He assisted Norwich's equalising goal, beating Adrián López Rodríguez on the right wing and providing a cross that was ultimately turned in by Wes Hoolahan.

[65] Morison's late strike from a tight angle drew Norwich level after they had trailed 3–2 with five minutes remaining.

[70] On the last day of the 2013 January transfer window, Morison signed for Championship club Leeds United as part of a swap deal.

[73] On signing Morison, the then-Leeds manager Neil Warnock said that "Steve meets all the requirements of the striker we've been looking to bring in.

[71] Morison made his Leeds debut on 9 February 2013, playing the whole match in the club's 2–2 draw against Wolverhampton Wanderers at Molineux.

[67] A day after returning for pre-season training with Leeds, on 28 June 2013, Morison joined former club Millwall, also of the Championship, on a season-long loan deal.

[78] Morison made 41 appearances during the loan agreement, of which 25 were starting, and scored eight times as Millwall finished the season in 19th-place in the Championship.

[81] Morison missed the opening games of the season through injury, making his first league appearance for Leeds in over a year as a substitute against Huddersfield Town on 20 September 2014.

[82] Morison rejoined League One club Millwall for a third spell on 4 August 2015, signing on a permanent basis for an undisclosed fee.

[93] He played over 300 games across his three spells with Millwall, scoring 92 goals in all competitions, which ranks him in third place in the club's all-time record goalscorers.

[98] Morison announced his retirement from playing with immediate effect on 18 October 2019,[99] in order to begin his coaching career at the academy of his first club, Northampton Town.

[102] In May 2010, it was identified that Morison was eligible to represent Wales due to Welsh ancestry – as his grandmother was born in Tredegar, near Ebbw Vale.

[4] He subsequently earned his UEFA Pro Licence and, after retiring as a player in October 2019, began coaching at the academies of former clubs Northampton Town and Millwall.

[111] His first match as caretaker manager was a 3–3 draw away at Stoke City with the team having been 3–0 down with 25 minutes remaining; the result ended Cardiff's club-record run of eight defeats in a row.

[122] Under Morison, Sutton's form would improve with the club winning four consecutive matches to briefly move out of the drop zone for the first time since August.

[124] Ahead of the 2008–09 season, Stevenage manager Graham Westley sent Morison to a training camp to work on his turn of pace.

[124] In May 2010, Millwall manager Kenny Jackett said that Morison "has a lot of strength and pace, which he uses on defenders perfectly", as well as referring to him as a "physical threat" because of his aerial ability.

[126] However, he said he "could not handle the early starts" and subsequently got "an easier job indoors" doing administration work in an office, where he met his wife; they have had a son together, called Fenton.

[128] In January 2013, Morison set up a greyhound racing syndicate alongside his former strike partner at Norwich City, Grant Holt.