EUGENE — It was only a matter of time before the Oregon State offense got going Thursday night.
Cole Stringer held No. 1-ranked Oregon State scoreless for three innings, but the Beavers pounded out six runs over the final six frames — including three in the eighth — to come away with 6-1 series-launching victory over Oregon at PK Park.
Oregon State improved to 39-4 overall and 22-3 in the Pac-12 -- and clinched at least a share of the league title.
Oregon fell to 26-19, 9-13.
"It's always good to get wins in this conference. It's a tough conference," said OSU coach Pat Casey, who collected the 999th victory of his career. "It's hard to win in this league. It's really hard to win on the road, especially in an opening game, so I'm proud of my guys for the way they played."
The game initially figured to feature probably the two best pitchers in the Pac-12 in Oregon's David Peterson and Oregon State's Luke Heimlich. Peterson holds the Oregon single-season record for strikeouts (117), while Heimlich is the reigning Pac-12 pitcher of the week and has the lowest ERA in the conference among starters (0.76).
However, Peterson was pushed back a day in the rotation, having pitched Saturday instead of Friday against Washington State due to a rainout. He would have been throwing on two days shorter rest than normal if he had gone against the Beavers on Thursday.
"I'm sure a lot of people were looking forward to the Heimlich-Peterson matchup," Oregon shortstop Kyle Kasser said. "Usually Petey comes out and sets the tone for us, but at the same time, we expect whoever is going for us to do the same thing."
Oregon was forced to go with Stringer on three days rest after he threw 5 1/3 innings on Sunday.
In the fourth, OSU catcher Adley Rutschman hit a solo home run over the right-center field wall. Three batters later, third baseman Michael Gretler homered off Stringer, a sophomore from Central Catholic High, to extend the lead to 2-0 before a crowd of 2,209.
"We moved him up in the order. The guy is really a competitor," Casey said of Rutschman, who batted fifth on Thursday. "He's a great athlete."
Rutschman, who came into the game batting .223, went 3 for 5 with two RBIs and a stolen base.
"Hitting is a process," the freshman from Sherwood High said. "I've just been sticking with my process and working throughout the season, and now it's hopefully starting to turn around."
After an RBI single by Rutschman put Oregon State up 3-0, Heimlich headed back to the mound for the bottom of the fifth.
The Ducks got consecutive singles from Taylor Travess, Morgan McCullough and Kasser to load the bases with one out. Heimlich then hit Oregon center fielder Jake Bennett to bring home Travess.
But Heimlich was able to force Oregon third baseman Spencer Steer to hit into a 4-6-3 double play that ended the inning.
"Give credit to (the Ducks). They swung the bat," Casey said. "(Heimlich) was elevated all game and didn't have his stuff. He really battled. To not have good stuff and give up one run against a good club in their yard says something about him."
Heimlich finished strong in the sixth by striking out the side. He gave up seven hits (tying his season high) in six innings, but struck out seven and improved to 8-1.
"Pretty early on, I could tell I didn't have my command. I knew I really needed to battle down and get outs where I could," Heimlich said.
Oregon State reliever Brandon Eisert replaced Heimlich in the seventh and was lights out in his three innings, giving up two hits and no walks while striking out four.
Eisert, a freshman from Aloha High, got more than enough insurance runs when the Beavers strung together three runs in the eighth to take a 6-1 advantage.
It looked that the Ducks would get out of the inning when Oregon State second baseman Nick Madrigal grounded to second baseman McCullough with runners on first and second. McCullough touched the base to get the force, but a poor throw to first allowed the inning to continue.
Oregon State right fielder Jack Anderson took advantage by hitting a two-run double inside the left-field line.
Game 2 of the three-game set will be at 7 p.m. Friday. A win would give OSU the outright Pac-12 crown; Stanford and UCLA are tied for second at 13-8.
The Beavers have yet to decide who will go to the hill.
"We were thinking we either go back with (Jordan) Britton or maybe (Jake) Mulholland," Casey said.
Britton went 5 2/3 innings against Oregon on May 2 and allowed two hits and one run in a 4-1 OSU victory.
"We'll go meet in the office when we get back and make that decision," Casey said.
One thing is for certain: The Beaver batters will have their work cut out for them as they get set to face Peterson.
Casey, asked if Peterson would be the best pitcher that the Beavers have faced, replied: "If he's not, I don't want to face the guy that's better than him."