PULLMAN - Stanley Havili did a lot of everything and Southern California did what it usually does against Washington State, rolling to an easy victory.

Havili ran for 80 yards on four carries, caught five passes for 107 yards and scored two touchdowns, and No. 20 USC pounded Washington State 50-16 on Saturday.

USC (4-0, 1-0 Pac-10) had been up and down in wins over Hawaii, Virginia and Minnesota. But against the worst team in the Pac-10, the Trojans didn't struggle much in gaining 613 yards.

Washington State (1-3, 0-1) lost its 12th straight game to an FBS opponent and lost to USC for the eight straight time. The last three have been particularly brutal, with USC outscoring the Cougars 193-36.

"We had a complete game for the first time this season," Havili said.

Coach Lane Kiffin wanted to add a qualifier.

"This is the closest we have played to a complete game," said Kiffin, who became the first USC coach since Jess Hill in 1951 to start 4-0 in his first season. "If you take out the three first half turnovers, it was a complete game."

Matt Barkley completed 16 of 25 passes for 290 yards and three touchdowns. But he threw two first-half interceptions, one that led to a WSU touchdown and helped keep the Trojans' lead at just 28-13 at halftime.

"Those turnovers make this win not feel so good," Barkley said.

But it felt even worse for Washington State, which tried a four-receiver passing attack against Southern Cal's vulnerable secondary.

WSU's Jeff Tuel completed 24 of 37 passes for 222 yards and a touchdown, but was intercepted three times. Jared Karstetter caught eight passes for 87 yards and two touchdowns.

"We moved the ball really well today," Tuel said, of the 323 yards of offense. But the Cougars have yet to score more than 23 points in a game.

Washington State did score on its opening possession of the game for the first time since the 2008 season.

"That gave us some confidence," defensive end Travis Long said.

Southern California blew the game open early in the second half, scoring the first two times it had the ball. USC has a 58-8-4 lead in the series that dates to 1921.

"We felt like we were in the game," Long said. But USC's 93-yard drive to open the second half was built on WSU mistakes that "killed us."

Allen Bradford rushed for 84 yards for USC, and the Trojans gained 285 yards on 39 carries, a 7.3 average, plus 328 yards passing.

"Our goal was to be 4-0, be healthy, and not worry about the scores," Kiffin said of the first four games. Now the competition gets tougher, starting with a game next week at Washington, which beat the Trojans last year.

USC led 21-7 after an action-packed first quarter in which it had the ball for 95 seconds and ran five plays.

Washington State took the opening kick of the game and marched down the field, scoring when Jeffrey Solomon took a handoff from running back James Montgomery and lofted a 29-yard pass to Karstetter in the end zone.

"We got the place fired up and rocking," Tuel said. "We were not going to lay down for these guys."

The Cougars then tried a pooch kick, giving Southern California the ball on its own 41. Havili ran 59 yards on the first play to tie the game at 7.

On the second play of the next series, Tuel threw the ball directly to USC cornerback Nickell Robey, who ran 25 yards untouched into the end zone for a 14-7 Trojans' lead with 11:07 left in the first.

Havili turned a short pass from Barkley into a 58-yard gain on USC's next possession. Barkley hit Robert Woods for an 11-yard touchdown pass and a 21-7 lead.

USC's Wes Horton blocked a punt by Reid Forrest on the next series, and the Trojans recovered on the WSU 10. But Barkley's pass on the first play was intercepted by Deone Bucannon on the 1.

Alex Hoffman-Ellis intercepted Barkley early in the second quarter, and the Cougars went 45 yards, with Karstetter making an over the shoulder catch from Tuel for a touchdown. Nico Grasu's conversion kick was blocked.

Marc Tyler ran over from the 2 to give the Trojans a 28-13 lead with 1:50 left in the first half. Tuel threw just one interception through the first three games, but was intercepted three times in the first half.

The Trojans went 93 yards in just four plays on the opening drive of the second half, with Brice Butler catching a 7-yard touchdown pass from Barkley. They went 98 yards on their next possession, scoring on fourth-and-5 from the WSU 7 when Barkley connected with Ronald Johnson for a 43-13 lead with 4:02 left in the third.

Havili caught a 22-yard touchdown pass from backup quarterback Mitch Mustain early in the fourth.