Dylan Riley rushed for a game-high 128 yards, including a pair of fourth-quarter touchdowns, and No. 21 Boise State scored 21 unanswered points to pull away for a 31-10 victory over Washington State in a Pacific-12 Conference game Saturday in Pullman, Wash.

Riley, who carried 13 times, scored on runs of 33 and 72 yards for the Broncos (6-1, 3-0 Pac-12), who won their sixth consecutive game. Sire Gaines added 64 yards rushing and a score on 10 attempts. Maddux Madsen completed 14 of 23 passes for 149 yards and a touchdown, with Rasean Jones making five catches for 69 yards.

Quarterback Owen Eshelman, making his second start for the Cougars (1-7, 0-4), was 21-of-40 passing for 191 yards with one interception. He also rushed for a team-high 33 yards on 23 attempts.

Madsen threw a 6-yard scoring strike to Cam Bates with 13:33 remaining to break a 10-10 tie. The go-ahead drive spanned 70 yards on 15 plays and took 7:14 off the clock. Madsen completed a 3-yard pass to Jones on fourth-and-2 from Washington State's 15-yard line to keep possession.

Boen Phelps intercepted an Eshelman pass on the ensuing drive, giving the Broncos the ball at WSU's 33. On the second play, Riley tallied from 33 yards out to put Boise State up 24-10.

After a Washington State punt, Riley scored on the 72-yarder with 6:26 left.

The Broncos took a 10-7 halftime lead on Canaan Moore's 28-yard field goal as time expired in the second quarter. Boise State moved 54 yards in eight plays in the final 46 seconds to set up the kick.

That came after the Cougars put together a 16-play, 73-yard touchdown drive, with Kirby Vorhees scoring on a 1-yard run behind left guard. Washington State converted two fourth-down plays on the drive.

The Broncos opened the scoring with 4:24 left in the first quarter on a 9-yard run up the middle by Gaines that capped a seven-play, 74-yard drive.

The Cougars tied the score at 10-10 on Jack Stevens' 47-yard field goal with 5:53 remaining in the third quarter.