USC freshman pitcher Mitch Hart gave up just two hits, but was charged with five earned runs in 3 1/3 innings when he walked six batters and hit another. In back-to-back innings, the Beavers (27-13, 10-8) were able to score multiple runs with minimal base hits.
They took a 2-0 lead in the third inning using two walks, a bunt single, a hit-by-pitch and a sacrifice fly. USC (30-12, 11-7) bounced back with a four-run fourth inning with all four of its runs scoring on non-hits (walk, sacrifice fly, squeeze bunt, sacrifice fly).
But Oregon State quickly loaded the bases with a single and two walks, leading USC Coach Dan Hubbs to go to his bullpen. Bernardo Flores walked home a run before giving up a two-run single to Trever Morrison. Another run scored later in the inning on a passed ball. The Beavers tacked on single runs in their final three at bats leaving themselves plenty of wiggle room even when USC scored two runs in the ninth inning.
The Trojans lost Saturday's game, 3-2, when pinch-hitter Billy King grounded a ball through the right side, allowing catcher Dane Lund to score the winning run in walk-off fashion. Lund was a thorn all game for USC. He never made an out as a hitter, going three for three with a walk.
The ninth-inning heroics followed a pair of strong starting efforts. USC junior Kyle Twomey allowed two runs on four hits in seven innings while Beavers' freshman Drew Rasmussen went eight innings, giving up two runs on seven hits.
Rasmussen's effort was needed after USC pummeled the Pac-12 leader in earned run average, Andrew Moore, for six runs in 6 1/3 innings en route to an 11-3 win to open the series. Timmy Robinson had three hits and drove in three runs. Duke transfer Angelo La Bruna drove in four runs, including hitting his first homer as a Trojan.
Moore may have struggled, but his counterpart, Tyler Gilbert, did not. Thrust into the Friday night role and making his first Pac-12 start, Gilbert gave up just four hits. He struck out 10 Beavers and earned his third win.
USC's top-of-the-lineup duo of Bobby Stahel and Garrett Stubbs combined for 10 hits and seven runs in the series. However, Oregon State was able to hold Stahel hitless on Saturday, snapping his 22-game hit streak.
The Trojans will try to respond to the series loss on Tuesday when they host traditional powerhouse Cal State Fullerton at 6 p.m. PDT.