After a brief civil service career in Dublin and London, during which he acted in amateur dramatic societies (as a civil servant, he couldn't perform in public under his own name, hence F.J. McCormick, a name he chose at random since he liked the sound of it), he became a member of the Abbey Theatre (now the National Theatre of Ireland) company in 1918. Over the next 30 years, he appeared in over 500 plays, being particularly celebrated for his performances of works by Sean O'Casey (he created the roles of Joxer in Juno and the Paycock and Fluther Good in The Plough and the Stars); he was considered the greatest and most versatile Irish actor of his generation. He appeared in only three films, despite many offers: this because of his great loyalty to the Abbey and to the young Irish state, and also because acting in John Ford's bowdlerised film version of The Plough and the Stars (1936) left him profoundly disaffected with the Hollywood system. He married his fellow Abbey actress Eileen Crowe in 1925.