Bias scored 18 of her points in the first half for the Cowgirls (10-0), who matched the school's previous best start in 1995-96.
Liz Donohoe added 18 points for Oklahoma State, which will meet San Diego State on Sunday. Toni Young had 16 points and 12 rebounds while Brittney Martin scored 12 points and grabbed 11 rebounds. OSU owned a 53-32 edge on the boards.
The Cowgirls have won 16 straight games, the longest winning streak in the nation. They won the WNIT last season.
Temi Fagbenle led Harvard (7-4) with 18 points and 10 rebounds. Christine Clark added 15 points for the Crimson.
It was the first meeting between the schools.