From 1893 to 1894 he toured Britain and Ireland with Sir Augustus Harris's Italian Opera Company to sing the principal tenor roles in "Cavalleria rusticana", "Faust", "Pagliacci", "Carmen", "Lohengrin" and "Die Meistersinger", among others, his strong Heldentenor voice being particularly appropriate for the latter two roles. In 1894 he first appeared at Covent Garden Theatre. For three years, O'Mara was the principal tenor at Theatre Royal, Drury Lane, also appearing in the pantomime of "Jack and the Beanstalk" there. He then played in the pantomime "Aladdin" at the Prince of Wales Theatre, Liverpool. In 1896, he created the tenor lead, Mike Murphy, in Charles Villiers Stanford's opera "Shamus O'Brien", with Henry Wood conducting. After a tour of Britain and Ireland in "Shamus O'Brien", the Harris company brought the opera to America in 1897, where, with his new wife, the former Miss Power, O'Mara enjoyed great personal success. Throughout the rest of his career, Mike Murphy would remain one of O'Mara's signature roles.