The show would prove to be a long-term success, but in 1936, Cooper capitalized on the fame of Lights Out and resigned from NBC, moving to Hollywood, California, where he worked as a screenwriter for film studios.

Arch Oboler, who took over the writing of Lights Out when Cooper left, would suggest that Cooper was the first person to create a unique form of radio drama, writing, "Radio drama (as distinguished from theatre plays boiled down to kilocycle size) began at midnight, in the middle thirties, on one of the upper NBC floors of Chicago's Merchandise Mart.

He continued to make a living writing radio scripts for various network programs including The Campbell Playhouse, the sponsored successor of Orson Welles's Mercury Theatre.

The series was hosted by Chief Superintendent John Davidson, fictional curator of the Black Museum at Scotland Yard.

It featured an allegedly British cast and told stories inspired by artifacts held by the famous London crime museum.

As television became the dominant entertainment medium, Cooper experimented with various programs including Volume One, which he wrote and produced.