Appearing in well over one hundred films, and acting extensively on television into the 1970s, Qualen performed many of his roles with various accents, usually Scandinavian, often intended for comic effect. Three of his more memorable roles showcase his versatility. Qualen assumed a Midwestern dialect as Muley, who recounts the destruction of his farm by the bank in Ford's The Grapes of Wrath (1940), and as the confused killer Earl Williams in Howard Hawks' classic comedy His Girl Friday (also 1940). As Berger, the jewelry-selling Norwegian resistance member in Michael Curtiz' Casablanca (1942), he essayed a light Scandinavian accent, but put on a thicker Mediterranean accent as the homeward-bound Fisherman Locota in william Wellman's The High and the Mighty (1954)