Following the 2014 season, it was expected that Wallace would move up to the Xfinity Series with Joe Gibbs Racing in a full-time ride, with owner Joe Gibbs claiming they would have "a big program" for the young driver. After the team struggled to find sponsorship for more than 15 races, on December 8, 2014, Wallace announced he had been granted his request to leave JGR and seek other opportunities. Later, it was reported he had signed a deal to compete in the Xfinity Series for Roush Fenway Racing for 2015 with Chad Norris as his crew chief. On December 18, 2014, RFR officially announced that they had signed Wallace to compete full-time in the No. 6 Ford Mustang in 2015, with sponsors and crew members to be announced at a later date. On January 28, 2015, at NASCAR Media Day, it was announced that Wallace would drive the No. 6 Ford EcoBoost Mustang. Wallace started the season with a 12th-place finish at Daytona and earned 14 top-tens to finish 7th in the final point standings. He was beat by Daniel Suárez for Rookie of the Year by a single top-ten finish.