After training in France, Moore made her operatic debut at the Metropolitan Opera in New York City on February 7, 1928, singing the role of Mimì in Giacomo Puccini's "La bohème". She debuted at the Opéra-Comique in Paris on September 29, 1928 in the same role, which she also performed in a Royal Command Performance at Covent Garden in London on June 6, 1935. During her sixteen seasons with the Metropolitan Opera, she sang in several Italian and French operas as well as the title roles in "Tosca", "Manon", and "Louise". "Louise" was her favorite opera and is widely considered to have been her greatest role.