OSU made 7 of five its first 11 shots and was able to stay within shouting distance in the first half.
Poor shot selection (5 of its last 20) led to a 49-31 halftime deficit.
The deficit dwindled to 54-47 with 11:56 remaining but OSU got no closer in the second half.
Pittsburgh point guard Levance Fields had 17 points, six assists and three rebounds.
Oklahoma State was led by Marcus Dove's 17 points.
Terrel Harris had 16 points and nine rebounds, while Obi Munonelo added 11 points and six rebounds for the Cowboys (5-4), who suffered their 14th straight road loss.
They had won three in a row.
Pregnant Mila Kunis wins 'Best Villain' at MTV Movie Awards
'Happy' fan videos make Pharrell cry [VIDEO]