Moore intended to begin a concert career, but she made her debut at age 17 with the D'Oyly Carte Opera Company. There she created the leading role of Casilda in "The Gondoliers", the last great Gilbert and Sullivan hit, which opened at the Savoy Theatre on 7 December 1889. W. S. Gilbert asked her if she had ever acted. When she replied in the negative, he replied, "So much the better; you'll have less to unlearn!" She related her first-night experience: