After losing a fumble on their first series, Harrell led the Red Raiders to a touchdown on their next seven possessions. The Red Raiders (10-0, 6-0 Big 12) won their school-record 12th straight game.
Michael Crabtree, who scored in the final second in last week's win over then No. 1 Texas, scored three touchdowns Saturday against the Cowboys.
Kendall Hunter ran for 112 yards and a pair of scores for the Cowboys (8-2, 4-2).