Hungarian-born of German descent, Winkler began her career as personal secretary of Harry Warner, one of the founders of Warner Brothers. Through most of the silent era, Warner Brothers was strictly a film distributor, and Harry Warner was the man who made the deals. In 1917, Warner Brothers began distributing cartoons of Mutt and Jeff in New York and New Jersey. Warner was impressed with Winkler's talents, and when Max and Dave Fleischer, owners of Fleischer Studios, came to him with their series Out of the Inkwell, he gave it to Winkler and encouraged her to form her own distribution company, Winkler Productions, on a state's rights basis. In 1922, she signed a contract with Pat Sullivan Productions to produce Felix the Cat cartoons. This established her reputation as the top distributor in the cartoon world. It was a good thing, because at the end of the same year the Fleischer brothers, flush with success as a result of Winkler's work, left her to form their own distribution company, Red Seal Pictures. However much Sullivan helped Winkler's business, he and Winkler were constantly fighting. In September 1923, the renewal of his contract came up, and his unrealistic demands meant Winkler Pictures might have to survive for a while without its biggest star. Winkler viewed a pilot reel, called "Alice's Wonderland", submitted by then neophyte animator Walt Disney, the first entry in the "Alice Comedies" series. Winkler was intrigued with the idea of a live-action girl in a cartoon world, and signed Disney to a year-long contract despite the fact that the studio that made the cartoon was now bankrupt. Disney subsequently formed a new studio, Disney Brothers, which was the first cartoon studio in Hollywood and soon changed its name to The Walt Disney Company. Disney was helped by the tutelage of Winkler, who insisted on editing all of the "Alice Comedies" episodes herself. One of her suggestions was the addition of a suspiciously Felix-like character called Julius. This was apparently the "straw that broke the camel's back" for Sullivan, who signed with rival distributor E. W. Hammons of Educational Pictures in 1925. Winkler was the first female member of the Motion Picture Producer's Guild. To disguise her gender, she would sign letters "M.J. Winkler."
Marriage
In 1924, she married Charles B. Mintz, a film distributor who had been working for her since 1922. Soon after she had her first child and retired from the business, turning her company over to her husband. The couple had two children, Katherine and William.
Death
Margaret Winkler died on June 21, 1990 in Mamaroneck, New York. She was 95 years old.
