John Eric Winchester is a fictional character on The CW's series Supernatural, and the protagonist of the comic book spin-off series Supernatural: Origins. Developed by series creator Eric Kripke, the character is mainly portrayed by Jeffrey Dean Morgan. John is the father of Sam and Dean Winchester, the show's protagonists.

Answer this question: who did jeffrey dean morgan play on supernatural? Let's give stream of consciousness first:
The important part for answering this question is: Developed by series creator Eric Kripke, the character is mainly portrayed by Jeffrey Dean Morgan.
So, the final answer is John Eric Winchester.