Conversation so far:
What was Mercury Theatre?
The Mercury Theatre was an independent repertory theatre company founded in New York City in 1937 by Orson Welles and producer John Houseman.
What did Mercury Theatre do?
The Mercury Theatre produced theatrical presentations, radio programs and motion pictures.

Question: What role did Houseman play?
Self-contained rewrite: What role did Houseman play in the work done by Mercury Theatre?