Has Oklahoma ever played Ohio state in football?

Yes they have. They won 8 titles (either outright or co-champs) as members of the Missouri Valley Conference in these years: 1926, 1930, 1932, 1933, 1944, 1945, 1948, and 1953). They won a share of the Big 8 title in 1976. The official web page for the Cowboys says 10 conference titles, but I could only find 9. College Football Data Warehouse agrees with you. They have Oklahoma State winning 5 Missouri Valley championships and 3 co-championhips along with 1 Big 8 co championship.