Yeats, who had a later career as a movie studio costume supervisor, died Nov. 11 at her home in San Clemente, said her daughter, Joan Young. Yeats had suffered three strokes in her later years.
She was 3 years old in 1915 when she was discovered by director Henry King at the Balboa Amusement Producing Co. in Long Beach, where her foster father was in charge of the studio zoo and her foster mother was an extra.
One day King was in a pinch and needed a young boy actor for a role in "The Maid of the Wild," a short film in which King also acted.
"I was there, and I had a Dutch bob so they dressed me as a boy," Yeats recalled in a 2001 interview with The Times.
King was impressed with the cute little girl's work in front of the camera.
"He thought she had a great screen presence — she was a natural — and he wanted to promote her," said Jean-Jacques Jura, who interviewed Yeats for his 1999 book "Balboa Films: A History and Filmography of the Silent Film Studio," co-written with Rodney Norman Bardin II.
King launched Baby Marie to stardom in "Little Mary Sunshine," a 1916 film written especially for her.
"Little Mary Sunshine" was the first in a series of feature movies made at the Balboa Studios starring Baby Marie Osborne.
One newspaper story at the time was headlined, "Baby Marie Osborne, the Youngest Leading Woman in the World."
Of her performance in "Little Mary Sunshine," the writer of the article observed that "she never overdoes the saccharine stuff," and "her utter unself-consciousness of herself is a revelation in art."
"She was a huge success," said Jura.
The young film star's fame extended to Europe, and she went on national personal appearance tours. There were even Baby Marie dolls and paper dolls.
Balboa Films took pains to ensure the proper treatment of its prized child star on the lot, as Jura and Bardin discovered while researching their book. Among the studio's directives:
"She is not to be teased at any time."
"She is not to be shouted at nor addressed in slang."
"She is not to be coddled nor handled unnecessarily. The idea of the management being hands off. You must adore her from afar."
In 1917, after Baby Marie's contract expired at Balboa Films, Jura said, the Osbornes and a business partner took over the old Kalem Studios in Glendale, which they renamed Diando Studios, to make their own movies starring their little girl.
Baby Marie's glory days as a child star, alas, were short-lived, the end coming after she starred in the 1919 comedy short "Miss Gingersnap."
"There was a trust fund, but I never seemed to have received anything," she told The Times in 2001. "It doesn't matter. My foster mother bought me beautiful clothes. They had a nice life while it went on. They were divorced when I was maybe 7 or 8. I went back and forth between them. Then I lived with my foster father."
She was born Helen Alice Myres in Denver on Nov. 5, 1911, and soon became the foster daughter of Leon and Edyth Osborn. (They renamed her Marie and later added the "e" to their name.)
"I was [taken out of] the Colorado state home for dependent children when I was about 3 months old," Yeats told The Times in 2001. "My foster father managed a five-cent [movie] theater in Colorado Springs. I don't know why my foster parents went to California."
In the 1930s and '40s, Yeats occasionally had uncredited bit parts in films, as well as working as a stand-in for Ginger Rogers, Deanna Durbin and Betty Hutton.
Beginning with an apprenticeship at Western Costume Co. in 1952, she had a more than two-decade career as a studio costumer and costume supervisor on films such as "Guys and Dolls," "Spartacus," "Cleopatra" (she was in charge of Elizabeth Taylor's wardrobe), "The Way We Were," "Mame" and " The Godfather, Part II."
"I must be frank with you: I much preferred it to acting," Yeats, who retired in 1976, said in the Times interview. "I've had a fascinating, wonderful life."
Yeats' 1931 marriage to Frank Dempsey, with whom she had her daughter, ended in divorce in 1937. Her 1945 marriage to Murray Yeats ended with his death in 1975.
In addition to her daughter, Yeats is survived by five grandchildren.
A funeral Mass will be held at 10 a.m. Friday at Our Lady of Fatima Catholic Church, 105 N. La Esperanza, San Clemente. Burial will be at noon at Mission San Luis Rey, 4050 Mission Ave., Oceanside.