Randolph Scott, a versatile leading man who later specialized in playing the quiet-talking, fast-drawing hero of westerns, died today at his Bel-Air home. He was 89 years old.

The actor's son-in-law, Sam Tyler, said Mr. Scott died in his sleep. He had been ill in recent years with a weak heart and several bouts of pneumonia.

Mr. Scott, born in Virginia, entered films in 1929 and became a leading man in the mid-1930's with such movies as ''She,'' ''The Last Round-Up,'' ''The Last of the Mohicans,'' ''High, Wide and Handsome'' and ''Jesse James.'' He also appeared in such musicals as ''Roberta'' and ''Follow the Fleet,'' both with Fred Astaire and Ginger Rogers, as well as in such screwball comedies as ''My Favorite Wife'' with Irene Dunne and Cary Grant.

During World War II and after, Mr. Scott portrayed military heroes in such films as ''Corvette K-225,'' ''Bombardier,'' ''Gung Ho!'' and ''China Sky.''

But his most lasting career was in westerns. He starred in about two dozen, including ''Santa Fe,'' ''Fort Worth,'' ''Man in the Saddle,'' ''Man Behind the Gun,'' ''Ten Wanted Men,'' ''Ride Lonesome'' and ''Comanche Station.'' One of his films, ''Sugarfoot,'' became a television series starring Will Hutchins. Laconic On and Off Screen

''All the old movies are turning up on television,'' he said upon retiring in 1963, ''and frankly, making pictures doesn't interest me too much any more.''

His last film was ''Ride the High Country'' in 1962, in which he starred with another longtime western hero, Joel McCrea, under the direction of Sam Peckinpah.

Mr. Scott, slender and 6-foot-2, was as laconic off screen as he was in his westerns. ''Frankly, I don't like publicity,'' he said in a 1961 interview. ''I always remember something that David Belasco said and had incorporated in the contracts of his stars. His theory was, 'Never let yourself be seen in public unless they pay for it.'

''To me, that makes sense. The most glamorous, the most fascinating star our business ever had was Garbo. Why? Because she kept herself from the public. Each member of the audience had his own idea of what she was really like. But take the other stars of today. There is no mystery about them. The public knows what kind of toothpaste they use, whether they sleep in men's pajamas and every intimate fact of their lives. When I read publicity about them, I can tell just which press agent they employ.''

From 1950-53, Mr. Scott was among Hollywood's Top 10 box office draws.

Other western hits were ''Gunfighters,'' ''Coroner Creek,'' ''The Doolins of Oklahoma,'' ''The Nevadan,'' ''Wild Horse Mesa,'' ''The Thundering Herd,'' ''Belle Starr,'' ''Virginia City,'' ''Belle of the Yukon'' and ''Colt .45,'' which also became a television series. He Was Seldom the Outlaw

In ''The Doolins of Oklahoma,'' Mr. Scott played an outlaw for a change. Generally, though, the cowboys he played appeared on the scene ''to clean up the town.'' He did so in ''Abilene Town,'' ''Trail Street,'' ''Albuquerque,'' ''The Walking Hills'' and ''Carson City,'' among others.

Mr. Scott once said of western pictures: ''They have been the mainstay of the industry ever since its beginning. And they have been good to me. Westerns are a type of picture which everybody can see and enjoy. Westerns always make money. And they always increase a star's fan following.''

Born Randolph Crane on Jan. 23, 1898, in Orange County, Va., Mr. Scott was educated at Georgia Institute of Technology and the University of North Carolina. He enlisted in World War I by lying about his age.

After the war, he came to California and enrolled at the Pasadena Playhouse, spawning ground of many future stars. He began by playing a bit role in ''The Far Call'' in 1929.

Mr. Scott and his wife, the former Patricia Stillman, were married 43 years ago Tuesday.

He is survived by his wife, a son, Christopher Scott, a daughter, Sandra Scott Tyler, and three grandchildren.

George Scott