LOS ANGELES, Dec. 27— Betty Garde, an actress who played roles in hundreds of radio dramas and portrayed Aunt Eller in the original Broadway production of ''Oklahoma!,'' died on Monday. She was 84 years old.

Miss Garde died at a Sherman Oaks hospital, said Elliott Reid, a longtime friend.

The actress, whose given name was Katherine Elizabeth Garde, was born in Philadelphia and began her stage career in the early 1920's. She played character roles in a number of Broadway productions, including ''The Social Register'' and ''The Primrose Path.''

In the 1930's she began work in radio, appearing on such programs as ''The Eddie Cantor Show,'' ''Perry Mason'' and ''The Fat Man.'' She was probably best known as the wife of the title character in ''Lorenzo Jones'' and as Mrs. Wiggs in ''Mrs. Wiggs of the Cabbage Patch.''

Miss Garde also worked on several Orson Welles radio specials and appeared regularly in the dramatic anthology ''Theater Guild on the Air.''

There are no immediate survivors, Mr. Reid said.