NORMAN, Okla. -- Oklahoma needed something to go right defensively.

Tulane's spread option was carving up the No. 2 Sooners on the ground for most of the game's first 20 minutes Saturday night, but for the second consecutive week, sophomore cornerback Parnell Motley came up with a game-changing play.

Motley's 77-yard interception return for a touchdown turned the tide from what was a tight game and Oklahoma blew the game open from there to win 56-14 and stay undefeated.

A week earlier against Ohio State, it was Motley's interception that helped the Sooners put that game away.

After seeing virtually no time on defense as a freshman, Motley is becoming Oklahoma's defensive playmaker.

"The ball's going to find its way into the guy's hands," Sooners linebacker Ogbonnia Okoronkwo said. "He's a playmaker."

That play put the Sooners up for the first time in the game and after the Green Wave had scored on their first two drives, they didn't score again the rest of the way.

"We didn't respond very well," Tulane coach Willie Fritz said. "As a team, they score so many darn points and they're so potent with their receivers, running backs and obviously you have a potential Heisman Trophy winner at quarterback. We didn't respond very well."

While Motley came up with the big play defensively, that Heisman contender came up big once again.

Sooners quarterback Baker Mayfield had a big game once again, throwing for 331 yards and four touchdowns to continue a blistering start to the season.

Through three games, Mayfield is 63 of 82 for 1,046 yards and 10 touchdowns with no interceptions.

Mayfield once again spread the ball out, hitting eight different receivers in the game and throwing touchdown passes to three different players.

Freshman CeeDee Lamb had four catches for 131 yards and two touchdowns, including one for 82 yards early in the game to answer Tulane's quick start.

Lamb also added a 22-yard touchdown reception later but was ejected for targeting early in the second quarter for a hit on Green Wave free safety Taris Shenall.

"We expected it to be overturned," Sooners coach Lincoln Riley said. "I still don't know. Based on what I saw and the way we've been coaching our guys, it shouldn't have been called. We'll get the interpretation from the conference."

With Lamb out the rest of the way, Marquise Brown became Oklahoma's big-play target. Brown had six catches for 155 yards and a touchdown -- an 87-yard score from backup quarterback Kyler Murray late in the game.

Oklahoma had 631 yards of total offense. The Sooners' 197 rushing yards were their most so far this season.

While the Sooners' offense was once again running on all cylinders, Tulane's spread option gave Oklahoma fits early before the Sooners settled in late in the first half.

The Green Wave's Dontrell Hillard and Johnathan Brantley hurt the Sooners early as Tulane rushed for 184 yards in the first half but managed just 53 yards on the ground in the second half. Hilliard finished as the game's leading rusher with 104 yards.

"I think this can be a game in six or seven weeks that can help you out a little bit," Fritz said after his team dropped to 1-2. "You've just got to keep battling, keep fighting. I thought we did a very good job of that in the first half."

Oklahoma's defense, after holding Ohio State's offense in check a week earlier, struggled from the start.

The Sooners turned the ball over on their initial drive, and the Green Wave drove 65 yards on eight plays to take the lead.

Tulane grabbed the lead again late in the first quarter after a nine-play, 75-yard drive.

While the Green Wave's two scoring drives were extended, Oklahoma struck quickly with a pair of first-half touchdown catches by Lamb.

Then Motley jumped in front of Jacob Robertson Jr. and intercepted a pass from Brantley, returning it for a touchdown. Cornerback Jordan Thomas helped Motley finish off the defensive score with a block on Brantley at the Tulane 31.

Brantley finished 5 of 9 for 43 yards.

NOTES: Sooners DT Matt Romar left the game on the third OU defensive play of the game and did not return. Romar was replaced by Marquise Overton and Dillon Faamatau. ... Tulane QB Jonathan Banks, who was injured early in a loss to Navy a week before, did not play. Johnathan Brantley started in his place. ... Oklahoma OG Cody Ford and S Robert Barnes did not play after suffering injuries a week earlier against Ohio State. ... Tulane RB Dontrell Hilliard surpassed the 2,000-yard career rushing mark in the first half. ... The Sooners open Big 12 play next Saturday at Baylor. ... Tulane hosts Army the same day.