PROVO, UT -- Luke Staley threw himself a nice birthday party and the Brigham Young defense showed it should be taken as seriously as the Cougars' prolific passing offense.

Staley had three touchdowns on his 19th birthday and Brigham Young's defense was dominant through three quarters before sending in the substitutes as the No. 25 Cougars beat No. 23 Colorado State 34-13 on Thursday night.

Kevin Feterik threw for two touchdowns in the Mountain West Conference's first game. One went to Staley, Oregon's high school player of the year last season who chose BYU (2-0, 1-0 MWC) over the likes of Nebraska, UCLA and Washington so he could play with his older brother, defensive back Dustin Staley.

"I came here because I have a brother who's playing," Luke Staley said. "I've always wanted to play with him and I've never had that chance. I thought it would be a unique experience."

Staley didn't have glamorous numbers: 14 carries for 65 yards and three catches for 35 yards. But he delivered when asked.

"He doesn't play like a freshman, does he?" Feterik said. "He's our starting halfback and he's a big part of our game plan. Once we get up 21 or 24 points, we'll always want to milk the clock."

The Cougars showed Colorado State (2-1, 0-1) what it feels like on the losing end of a blowout. The Rams, unranked in the preseason, broke into the Top 25 after a 41-14 victory over then-No. 14 Colorado.

Safety Erik Olson said the difference against the Buffaloes was that the Rams were making big plays.

"I had a pick in my hands and I dropped it," Olson said. "In any kind of a big game, the seniors need to make plays."

Colorado State didn't have Kevin McDougal, who rushed for 190 yards against the Buffaloes and 147 before a hamstring injury forced him out of last week's victory over Nevada.

It probably wouldn't have made a difference against BYU's fierce defense. The Rams had 129 yards, including just 15 rushing, through three quarters before scoring two meaningless touchdowns in the fourth.

"The way we were playing, they could have had Herschel Walker and we still would have won," said BYU linebacker Rob Morris.

Only the loss of Morris, a Butkus Award candidate, was reason for concern. Morris left in the third quarter with an abdominal strain but later said he expects to play Sept. 25 against Virginia.

"It will be a long week off so I'll be ready to go next week," Morris said. "I've had worse."

For the second straight week, Feterik looked composed as he directed the BYU offense. After throwing for 501 yards and three TDs against Washington, he was 28-of-37 for 310 yards and no interceptions this week.

"I'm not surprised about the way things are going for me because this is how it was in spring practice," Feterik said.

BYU set the tone on the opening possession, when Feterik led a 79-yard, 15-play drive capped by Staley's 1-run run at the 7-minute mark.

Feterik scrambled on third-and-18 for a 9-yard gain to the Rams 19. He was hit as he reached the sideline by Rick Crowell, who was penalized for a late hit that gave BYU a first down at the 9.

It got out of reach in the second quarter. After Staley's 7-yard pass from Feterik gave BYU a 14-0 lead, the Rams couldn't catch a break.

The Cougars fumbled twice during their third scoring drive, including an apparent turnover near midfield by running back Naufahu Tahi that Colorado State's Terrence Gibson returned inside the BYU 15.

However, officials ruled Tahi down.

On the next play, Feterik threw 27 yards to Ben Horton, who fumbled as he was tackled. The ball bounced into the arms of BYU's Chris Hale, who added another 5 yards to make it a first down at the Colorado State 25.

Six plays later, the Rams came hard with a blitz. Feterik stayed cool and threw a swing pass over the defenders' arms to Jaron Dabney, who raced into the end zone for a 15-yard touchdown, giving the Cougars a 21-0 halftime lead.

In the third, BYU added a 38-yard field goal by Owen Pochman and Staley's last TD, a 5-yard run that made it 31-0.