STANFORD, Calif. (AP) -- Brian Allen scored on 37- and 20-yard runs in the fourth quarter as Stanford beat Oregon State 21-17 Saturday in a matchup of two of the nation's top five offenses that degenerated into an exchange of turnovers.

Allen's 20-yard touchdown with 6:33 left gave Stanford a 14-10 lead, its first of the game. Roddy Tompkins caught a 69-yard scoring pass for Oregon State on the next play, but Allen responded with his 37-yard TD run with 3:45 remaining.

Stanford (4-2, 4-0 Pac-10) won despite four turnovers, including two fumbles by tailback Kerry Carter within yards of the Oregon State goal line. The Cardinal have won their first four conference games for the first time since 1970.

Oregon State (3-3, 0-3), trying for its first winning season since 1970, committed three turnovers -- bringing its total to 14 in the last three games, all losses.

Oregon State tailback Ken Simonton, who entered the game third in the nation in rushing with 158 yards per game, was held to 115. He fumbled twice near the Stanford goal line, and was stopped on fourth-and-goal from the Stanford 1.

Stanford entered the game fourth in the nation in total offense and fifth in scoring offense with 40.4 points per game. Oregon State was fifth in total offense and had averaged 34.4 points per game.

Jonathan Smith threw two scoring passes for Oregon State, the 69-yarder to Tompkins and a 5-yarder to Robert Prescott. Ryan Cesca added a 34-yard field goal.

Todd Husak, returning after missing most of the past two games with bruised ribs, had a 41-yard scoring pass to DeRonnie Pitts for Stanford. But Troy Walters, who needed 13 receptions to set the Pac-10 career record, was held to three.

After a scoreless first period, the Beavers capped a 15-play drive with the scoring pass to Prescott early in the second quarter. And a 66-yard punt return by T.J. Houshmandzadeh put Oregon State in position for another score.

But Simonton, who had scored 16 touchdowns in his previous six games, dropped a handoff at the Stanford 7 for just his second fumble of the season.

An interception by Jonathan Jackson helped get the Beavers in scoring position again a few minutes later, but Simonton was stripped of the ball at the Stanford 6 with 24 seconds left in the half.

And in the third quarter, the Beavers got within inches of the Stanford goal line before Simonton was stopped on a fourth-down run as Oregon State coaches frantically tried to get their team to call a timeout.

Stanford then marched nearly the length of the field before Kerry Carter fumbled at the Oregon State 6. But, on the first play after a punt, Husak found Pitts behind the Beavers' defense to tie the game late in the third quarter.

A 35-yard pass from Smith to Martin Maurer got the ball to the Stanford 1 again in the closing minutes of the third quarter.

Simonton was stopped on first down. He appeared to score on the next play, but Oregon State was penalized for an illegal shift. Smith was sacked at the 17 and then threw an incompletion before Cesca's field goal.

Allen then took over, scoring twice on runs up the middle on which he avoided or broke through would-be tacklers.