After moving briefly to London, McCormick returned to Dublin, where he worked in the Civil Service. He also took acting roles in the Workmen's Club on York Street, and for the first time under the pseudonym by which he became known for roles with the
Queen's Theatre, Dublin. McCormick acted in over 500 plays at the Abbey Theatre, becoming particularly associated with the plays of
Sean O'Casey staged there. Of his performance as Seumus Sheilds in
The Shadow of a Gunman, O'Casey said that the actor had created a character greater than that O'Casey had written. He played Capt. Brennan in the filmed version of O'Casey's
The Plough and the Stars but it was his return to film in
Carol Reed's
Odd Man Out (1947) that saw him singled out for praise in contemporaneous reviews. The
Irish Times wrote that "the acting of the Irish players was unremittingly professional, and, in the case of F. J. McCormick, as Shell, a weak-minded and elderly corner-boy, quite outstanding."
The Times of London found "it is Mr. F. J. McCormick as a sly, bird-like creature, who stops just the right side of informing, who catches most surely at the imagination." In their review of the film
Hungry Hill (also 1947),
The New York Times wrote, "As the butler who served John Brodrick, his sons, and their sons in turn, the late F. J. McCormick is truly magnificent, giving an even more subtle portrayal of Irish character than he did as the wily tramp in
Odd Man Out." == Later life and death ==