He was a New Democratic member of the Legislative Assembly of Ontario from 1990 to 1995 representing the riding of London South.
He practiced law for 10 years before entering political life and received the Quebec Bar Prize in 1977.
Winninger ran for the Ontario legislature in the 1985 provincial election, finishing in third place against Liberal Joan Smith in the riding of London South.
In 1992, he passed a private member's bill to save the Talbot Block, an historical site within London.
The NDP were defeated in the 1995 provincial election, and Winninger lost his seat to Progressive Conservative Bob Wood by over 7,000 votes.