 He joined Leyton Orient of the Third Division on 29 August 2003 on a one-month loan and made the first professional appearance of his career in a 4–1 home defeat to Cheltenham Town the following day, when he replaced Billy Jones at half-time.McCormack received the first red card of his career in a 0–0 draw with Lincoln City on 13 September, after committing two bookable offences.In late September, caretaker manager Martin Ling extended McCormack's loan until 1 November.