Kent Walton went 3-for-6 and extended his hitting streak to 13 games. Kasey Ko hit a three-run homer, and Dan Vargas went 3-for-5 and drove in three runs.

But one thing became clear by the fourth inning: BYU had a problem -- it couldn't stop Oregon State.

Two-time defending national champion Oregon State (9-7) may have had its struggles so far this year, but its lineup that features a .317 batting average, proved to be the real deal. The Beavers knocked around six different BYU pitchers for a 15-7 win on Monday afternoon at Miller Field.

"I think we got off to a little bit of a rough start. If we can try and avoid big innings we'll be in a whole lot better shape than when you give up a five-spot or a four-spot, that pretty well does you in," said BYU coach Vance Law. "I thought our guys competed pretty well; unfortunately, our consistency on the mound was not what we've come to expect."

What may give BYU hope in Game 2 of the series, scheduled for today at 1 p.m., is the way the Cougars hit the ball. BYU finished with 11 hits and could have made the game more suspenseful had the Cougars not left the bases loaded four times.

"We try to tell those guys that if we just get one hit here or there with the bases loaded, the game is a lot tighter than the final score indicates," Law said. "They made the pitches they needed to when it counted and we didn't. Hopefully, tomorrow we'll come back and play the way we're capable of, and if (starting pitcher) Jake Wortham gives us a shot to win, I know our guys will come swinging the bats. We'll be ready to go."

BYU trailed 9-2 after four innings, but charged back to cut the deficit to 9-6 with a four-run sixth inning. BYU leadoff man Sean McNaughton walked and scored on a Vargas double. Steve Parker walked and Ko cleaned the bases with a three-run homer to left that put a charge into the 2,110 fans at Miller Field.

Oregon State added a run in the sixth to go up 10-6 and then got out of a jam in the sixth. BYU had a chance to make things interesting when Ko stepped up to the plate with two outs with bases loaded, but OSU reliever Kraig Sitton struck him out to end the inning.

The Beavers didn't look back. Chris Hopkins led off the seventh with a pinch-hit solo home run to push the lead to 11-6 and OSU tacked on four more runs in the eighth to finish off BYU.

"After the first inning, when we matched them with almost identical innings, it all comes down to executing on the mound," Vargas said. "We had too many walks and it's tough to bounce back after that because you're on your heels. The game slows down and you lose momentum. College baseball is all about momentum and we just didn't execute on the mound, is what it comes down to."

Oregon State got busy early. Garrett Nash, a Jordan High School product, led off the game with a triple to right-center. Joey Wong followed with a single to right, scoring one. Jason Ogata kept it going with a single up the middle to leave runners at first and third. BYU starter Nelson Castleberry got Dan Robertson hit a sharp comebacker, which Castleberry turned into a 1-6-3 double play, but another run did score.

The Cougars got those runs back in the bottom of the first when Sean McNaughton greeted OSU starter Jorge Reyes with a single. He stole second and scored on a single from Vargas. Walton followed with a single to left and Vargas scored on a passed ball.

But the Beavers kept the pressure on. They chased Castleberry with five runs in the second. Drew George led off the inning with a single. Ryan Ortiz and Jordan Lennerton both singled. John Tommasini drew a bases-loaded walk, which signaled the end of Castleberry's day.

BYU called on Tyler Westensee, but Ogata greeted him with a double to score the fifth run of the inning and give OSU a 7-2 lead. The Beavers stretched their lead to 9-2 with two-run homer from Joey Wong in the fourth inning.

Nash went 2-for-4 for the Beavers and scored four runs. Ogata went 3-for-4 and drove in three runs. McNaughton went 2-for-3 for the Cougars and scored three runs.

Oregon State 250 201 140 -- 15 15 1

BYU 200 040 010 -- 7 11 2

Reyes, Starr (5), Sitton (6), Keller (8) and Ortiz. Castleberry, Westensee (2), Michon (4), Judd (8), Shutt (8), Leach (9) and Musso. WP-Starr (1-0), LP-Castleberry (2-3). 2B-Ogata (OSU), Robertson (OSU), Vargas 2 (BYU), Walton (BYU). 3B-Nash (OSU). HR-Wong (OSU), Hopkins (OSU), Ko (BYU).