[2][3] Her father had a stock company called the McKenzie Merry Makers, and was both an actor and director in stage productions and films.

[3] When she was ten weeks old, she appeared in an uncredited part in the film Station Content (1918) as Kitty's baby (played by Gloria Swanson).

[3][8] In 1938, she began to appear mainly in Western films, such as Ghost Town Riders (1938) as Molly Taylor (credited as Fay Shannon), and When the Daltons Rode (1940) as Hannah.

[9] In 1940, McKenzie appeared in the stage show Meet the People, which premiered in Los Angeles and ended up on Broadway.

[3] In 1941, the president of Republic Pictures, Herbert Yates, met McKenzie through a mutual friend, and after a screen test he signed her to a contract to appear opposite the cowboy singer Gene Autry in Down Mexico Way (1941) as Maria Elena Alvarado.

[3]During World War II, McKenzie left Republic Pictures to work in theater and pursue other projects.

McKenzie also toured extensively entertaining the troops alongside Bob Hope, Bing Crosby, Cary Grant, James Cagney, and old family friends Laurel and Hardy.

In the 1950s, she traveled to New York to study with Lee Strasberg at the Actors Studio, appeared on radio shows with Groucho Marx, and toured with the songwriter Harry Ruby.

[3] She appeared in the television series The Millionaire (1959) as Ruth Spencer, Mr. Lucky (1960) as Sheila Wells, The Tom Ewell Show (1960) as Emma Franklin, and Bonanza (1961) as Victoria Gates.

[3] In the 1960s, McKenzie returned to film in Breakfast at Tiffany's (1961) in a minor role and The Party (1968) as Alice Clutterbuck.

[11] Her brother-in-law was the actor and comedian Billy Gilbert[1] McKenzie died peacefully of natural causes in her sleep in Highland Park, Los Angeles on April 16, 2019.