2011/12 was a breakthrough season for Wallace, starting with a strong performance in the Premiership Sevens. Luke was dual registered to Esher, but World Cup call ups and two backrow injuries in the opening match of the season saw him starting for the club in rounds 2-7 of the Aviva Premiership. Harlequins were unbeaten during this period and Wallace attracted considerable praise, winning several man of the match awards, the first Etihad player of the month award and later being short listed for the Land Rover Discovery of the Year. Wallace made another 11 first team starts through the season and totalled 24 appearances. He signed for Championship side Coventry in the summer of 2019 after being released by Quins. He signed for Leicester Tigers ahead of the 2020–21 season. He rejoined Harlequins with immediate effect on 27 May 2021.