While continuing to present symphonic works and oratorios, the MF expanded into the field of opera; presenting open-air productions annually at usually the Percival Molson Memorial Stadium or at the Chalet atop Mount Royal.
Sir Thomas Beecham became the festival's chief conductor between 1941 and 1945, leading performances of Johannes Brahms's Ein deutsches Requiem, Edward Elgar's The Dream of Gerontius, Gabriel Fauré's Requiem, Charles Gounod's Roméo et Juliette, and Richard Wagner's Tristan und Isolde among other major works.