After leading 21-6, the Cowboys controlled the tempo for the rest of the first half to pull within three at the break at 42-39.
OU then led by five early in the second half until OSU used another run to take its first lead of the game when guard Keiton Page busted a three to make it 51-49.
From that point on, OU struggled to take command again, in large part because the Cowboys attempted 44 free throws and made 36 of those.
The Sooners were good from the charity stripe as well, but shot far fewer, making 24-of-26.
The Sooners drop to 4-4 in the conference, while the Cowboys improve to 4-5.
OU next takes on Texas at 8 p.m. Wednesday at Lloyd Noble Center.