He joined Second Division club Barnsley in May 1911 for a £25 fee, and performed well in pre-season. After their opening two fixtures brought criticism of the forwards, Barnsley omitted George Travers for the visit to Birmingham, moved George Lillycrop across to inside right, and gave Cornock his Football League debut at centre forward. Having justified his selection with two goals in a 3–1 win, he kept his place for five of the next six matches, and scored three more goals, but after two further appearances without scoring, Travers returned to the side and remained in it. Cornock was included in the 13-man training squad that prepared for FA Cup matches as Barnsley went on to win the competition, but did not make the team, although he did make a further six appearances in league competition. Barnsley chose not to retain Cornock's services, and he moved on to Midland League club Castleford Town.