SEATTLE - De'Anthony Thomas and Kenjon Barner sandwiched touchdown runs around Avery Patterson's 34-yard interception return for a score, and No. 2 Oregon used a third-quarter scoring blitz to shake Washington State for a 51-26 win on Saturday night.

Playing for the first time outside the Eugene city limits, the Ducks (5-0, 2-0 Pac-12) looked shaky at times in the first half and led just 23-19 at the break, but put together a nearly flawless third quarter to run away from the Cougars.

Thomas capped an 18-play drive to start the half with a 4-yard TD, then Patterson stepped in front of Connor Halliday's pass for Oregon's third interception return for a TD in two games. After Washington State (2-3, 0-2) went three-and-out, Barner scored on a 10-yard run to cap the 21-point spurt in just over 4 minutes.

Barner finished with four total touchdowns, including scoring runs of 22 yards in the first quarter and an 80-yarder in the fourth to go along with a 30-yard touchdown reception in the first half. His 195 yards rushing was the second-best rushing game of his career behind the 201 yards he had against Fresno State earlier this season.

The Ducks started the second-half with their longest scoring drive - by plays - of the season, a methodical 18-play march that ate up more than 6 minutes. They ran nine times and threw nine times on the drive and only three times faced third down. The last came from the Cougars 4 when Barner went in motion and the middle opened for quarterback Marcus Mariota to hand off to Thomas, who plowed in for his fifth rushing TD of the season.

Before Washington State got a chance to answer, Patterson was stepping in front of a pass intended for Gabe Marks and racing untouched the other direction for a score. Patterson joined Ifo Ekpre-Olomu and Troy Hill with returning interceptions for touchdowns this season.

After another three-and-out by the Cougars and a short punt, Oregon needed just seven plays for Barner to find the end zone for the third time and a 44-19 lead.

Barner put a cap on his night and an explosive second half when he escaped a pileup near the Oregon sideline and skirted free to run 80 yards early in the fourth quarter. His four total TDs is second behind a five-touchdown performance in 2010 against New Mexico. Mariota finished 21 of 32 passing for 169 yards, one touchdown and two interceptions in the first road start of his career.

Thomas had just six touches in the first half for a total of 33 yards and no play longer than 15. He got four touches on the first drive of the second half alone including the capping TD run. He also got his first kickoff returns of the season after most teams had refused to kick toward the speedy sophomore, but his longest return was 19 yards.

Washington State continued its series of playing once a year at the home of the Seattle Seahawks and for the foreseeable future it will be either Oregon or Oregon State as the foe. While the crowd of 60,929 was mostly crimson, there was plenty of green and highlighter yellow that made the trip north to see the Ducks first road game of the season.

Connor Halliday threw for 348 yards and Marquess Wilson had 12 catches for 182 yards and a touchdown to become Washington State's all-time leader in yards receiving. But the Cougars had no ground game finishing with (minus)-8 net yards rushing. Halliday was sacked seven times.

Washington State has proved a somewhat problematic foe for the Ducks the past few years. In 2010 in Pullman, the Cougars hung around into the third quarter before losing 43-23 and last year in Eugene, Washington State trailed just 15-10 at halftime before getting overrun in the second half.

Saturday night was the same, with the Cougars falling behind 20-3 late in the first quarter. Washington State scored 16 of the next 19 points, getting a 2-yard TD run from Carl Winston following Teondary Caldwell's 92-yard kickoff return, and Brett Bartolone's 26-yard touchdown reception to pull within 23-19 at the half.

The Cougars had a chance to go to the break with the lead, driving to the Ducks 17 late in the half before three straight sacks of Halliday forced Washington State to punt. That proved to be the Cougars last chance to hang around.