Nyorai kupfuurira kweiyi ndima - Pakazosvika 1937, Moorehead akanga abatana naOrson Welles' Mercury Players, somumwe wevatambi vake vakuru pamwe chete naJoseph Cotten. (Mukuonekwa pa "The Dick Cavett Show" musi waFebruary 19, 1973, akazivisa kuti, muna 1922, akanga asangana neWelles (makore gumi nemashanu mudiki wake) paakanga achingova nemakore manomwe paWaldorf-Astoria Hotel muNew York City.) Akaita mumitambo yake yeredhiyo ye "The Mercury Theatre on the Air", uye aive nebasa rekugara achipesana naWelles mune akateedzana "The Shadow" saMargo Lane. Muna 1939, Welles akatamisa Mercury Theatre kuenda kuHollywood, kwaakatanga kushandira RKO Pictures. Vazhinji vevatambi vake venhepfenyuro vakamujoinha, uye Moorehead akaita firimu rake rekutanga saamai vehunhu hwake, Charles Foster Kane, mu "Citizen Kane" (1941), inofungidzirwa nevatsoropodzi vazhinji vemafirimu seimwe yemafirimu akanakisa akamboitwa. Moorehead akaonekwa mufirimu rechipiri raWelles, "The Magnificent Ambersons" (1942), uye akagamuchira New York Film Critics Award uye Academy Award nomination
nokuda kwokuita kwake. Akaonekwawo mu "Journey Into Fear" (1943), kubudiswa kwefirimu yeMercury.