At the conclusion of 1939's "Wizard of Oz", the party of travelers finally gets an audience with the great and terrible Wizard of Oz, a huge, disembodied head given to imperious, bellowing pronouncements. Who played this strange character?
If you believe the Wizard of Oz blog (about 2/3rds of the way down the page) it states that:
the face was that of an anonymous actor in heavy make-up, lip synching to Morgan’s dialogue.
I can find no other source of information online, and being that everyone involved with the production is long gone I don't think you're going to find much else that answers this question conclusively.