Appeared frequently on Broadway between 1938 and 1959. Cook appeared as "Donn Cook" there between 1926 and 1930.
The play in which he starred that had the longest run, "The Moon Is Blue", was made into a film that caused a scandal in its time because it used the word "virgin" while showing a woman's bedroom. Cook played the same role that David Niven played in the 1953 film.