In what can be considered the "first sitcom," she appeared opposite George O'Hanlon, as Alice McDoakes, from 1948 to 1956 in the "Joe McDoakes" movie shorts.
She accepted the role in 1957's The Incredible Petrified World (1957) as a favor to its director, Jerry Warren, who was a former boyfriend. The actress originally cast in the lead couldn't do it and Warren couldn't find anyone else in time. He persuaded Coates to do it by telling her that the film would not be shown in California. However, after it was completed, she found out that Warren did indeed release the film in California, and she was told by at least one studio executive at Columbia that the film was so inferior and shoddy that the studio would not be hiring her again. On top of that, Warren never paid her.
The first actress to appear as Lois Lane with George Reeves. Although Noel Neill played Lois Lane before Phyllis, it was not with Reeves but rather Kirk Alyn.
Years after gaining fame as TV's first Lois Lane on "Adventures of Superman" (1952), she played Lois Lane's mother on an episode of "Lois & Clark: The New Adventures of Superman" (1993).