how many actors won an oscar in their first movie?

Answer 1

I would think not many. I think the old lady from Titanic did and Jessica Tandy as well. But not sure.

Answer 2

Julie Andrews, who didn't get to play Eliza Doolittle in My Fair Lady (1964), won a Best Actress Oscar playing the title role Mary Poppins (1964) in her film debut.
Shirley Booth won a Best Actress Oscar for Come Back, Little Sheba (1952); it's unfortunate that she made only a few films.
Ben Kingsley won the Best Actor Oscar playing the title role Gandhi (1982), the Best Picture that year, in his film debut.
Mercedes McCambridge in All the King's Men (1949), the Best Picture that year, earned a Best Supporting Actress Oscar opposite Broderick Crawford's Oscar winning Best Actor performance
10 year old Tatum O'Neal won the Best Supporting Actress Oscar for her screen debut in Paper Moon (1973), becoming the youngest winner ever in a competitive category
Harold Russell won two Oscars for his role in The Best Years of Our Lives (1946), the Best Supporting Actor and "for bringing hope and courage to his fellow veterans through his appearance"; the only time an actor has ever won two Oscars for a single performance
Eva Marie Saint in On the Waterfront (1954), the Best Picture that year, earned a Best Supporting Actress Oscar, opposite Marlon Brando's first Best Actor Oscar winning performance
Gale Sondergaard in Anthony Adverse (1936), earned a Best Supporting Actress Oscar
Miyoshi Umeki earned a Best Supporting Actress Oscar as Katsumi Kelly in Sayonara (1957)

Answer 3

I think Audrey Hepburn did in 'Roman Holiday'