On 11 August, Mason once again joined Bolton on loan, this time for the full season. On 16 September, Mason scored a second half hat-trick to earn Bolton their first win of the season at home to Rotherham United. This was the first hat-trick scored by a Bolton player in a competitive match since Fredi Bobic against Ipswich in 2002. On 21 January 2015 his loan was terminated by mutual agreement. Following his return from injury, Mason became a key part in new Cardiff boss, Russell Slade's plans towards the end of the 2014–15 season. The next season, Mason was rewarded the number 10 shirt and started the first 17 games of the season, with a return of 5 goals. During October, Cardiff suffered a barren run of goals scoring only 2, one where Mason scored the opener in a 1–1 with Brighton & Hove Albion. This resulted in Mason being dropped and new signing Tony Watt taking his place. On 28 January 2016, Mason signed a three-and-a-half-year contract with fellow Championship club Wolverhampton Wanderers for an undisclosed fee. He made his debut for Wolverhampton Wanderers on 2 February 2016 against Bolton, in a 2–2 draw at Molineux, in which he scored after three minutes of the game. The following season saw him score four further goals (including against Midlands rivals Birmingham and Aston Villa), to add to the three for Wolves in the second half of the previous campaign. However, after another new head coach arrived -–the fourth different one at Wolves within his short spell – Mason found himself out of his plans. On 23 August 2017, he was sent on loan to fellow Championship side Burton Albion until January 2018. He scored on his debut for Burton in a 1–1 draw with Sheffield Wednesday on 26 August 2017. After returning from his spell at Burton, he moved again on loan, this time to Major League Soccer side Colorado Rapids on 20 February 2018 until the end of the 2018 MLS season. On 12 July 2018, it was announced that Mason would end his planned season-long loan early and return to Wolverhampton. As the 2018–19 season began in England, Mason still remained outside of the first team plans at Wolves, who had by now been promoted to the Premier League. On 31 August 2018, he was loaned out to League One Portsmouth until January in a move which saw him again link up with Kenny Jackett who had signed him at Wolves. However, he made just a single appearance in the league for Pompey, appearing as a late substitute against Wycombe Wanderers.