[4] He made his debut in 1933 as an off-stage wind noise in The Tempest, and later played in Antony and Cleopatra (1934), Major Barbara (1935), As You Like It (1936), and the 1937 production of Hamlet starring Laurence Olivier.
[2][5] When Welles created the CBS radio series, The Mercury Theatre on the Air, Schnabel performed on episodes including the legendary broadcast, "The War of the Worlds".
[2] When Mercury Productions moved to the West Coast, Schnabel was one of the actors Welles cast in Heart of Darkness,[6]: 63–65 the film he first proposed for RKO Pictures before settling instead on Citizen Kane.
After elaborate pre-production the project never reached production because Welles was unable to sufficiently trim its budget to compensate for lost revenue in the wartime overseas market.
[2] His other stage credits include the 1938 Mercury Theatre production of The Shoemaker's Holiday; Eva Le Gallienne's 1944 revival of The Cherry Orchard; Peter Ustinov's Love of Four Colonels (1953); and A Very Rich Woman (1965) by Ruth Gordon.
He portrayed physicist Hans Bethe in In the Matter of J. Robert Oppenheimer (1969), appeared in Tom Stoppard's adaptation of Schnitzler's Undiscovered Country (1981), and was again on Broadway in Mike Nichols's production of Andrew Bergman's Social Security (1986).
They lived in Rowayton, Connecticut, for 45 years, founded the Rainbow Theater in Norwalk, and appeared there together in plays including T. S. Eliot's The Confidential Clerk and Friedrich Dürrenmatt's The Physicists.