CORVALLIS, Oregon -- Oregon State quarterback Sean Mannion passed for 328 yards and one touchdown and rushed for another score Saturday to pace the Beavers to a 29-14 victory over Portland State.

Trailing 14-13 at halftime, Oregon State forced turnovers on five of Portland State's first six possessions of the second half and took the lead for good on Garrett Owen's 26-yard field goal with 10:58 to play in the third quarter.

Owens added field goals of 25, 25, 31 and 23 yards to help the Beavers of the Pacific-12 conference avoid a season-opening loss at home to a FCS school for the third time in four seasons.

Oregon State's Storm Woods had 16 carries for 126 yards rushing. The Beavers finished with 505 yards total offense to Portland State's 215.

Portland State backup quarterback Paris Penn finished with nine carries for 112 yards and two touchdowns for the Vikings of the Big Sky conference, who managed only 40 yards offense in the second half.

Oregon State scored on two of its three first-quarter possessions with Owens hitting a pair of 25-year field goals to give the Beavers a 6-0 lead.

Portland State, with only 36 yards offense in the first quarter, crossed midfield for the first time on the first play of the second quarter when backup quarterback Paris Penn scored on a 58-yard run to put the Vikings in front 7-6.

The Beavers answered with a 10-play, 82-yard scoring drive with Mannion scoring on a 6-yard run to make it 13-7 with 9:36 to play in the second quarter. It was Mannion's second career rushing touchdown and first since his freshman season.

Penn put the Vikings back in front 14-13 with 5:38 remaining the half when he scored on an 11-yard run, capping a nine-play, 73-yard scoring drive that was aided by four OSU penalties, including a late hit out of bounds and a roughing the passer call.

At halftime, Oregon State had run 37 plays to Portland State's 27 and had a 285-175 advantage in total offense. The Beavers also had been penalized 10 times for 89 yards, while the Vikings were flagged once for 10 yards.

Portland State opened the second half with a turnover when wide receiver Darnell Adams attempted a deep pass that was intercepted by Oregon State's Ty Zimmerman at the Beavers' 40.

OSU then went 51 yards in eight plays, setting up a 26-yard field goal by Owens that put the Beavers back on top, 16-14.

The Beavers forced three more turnovers before the end of the third quarter, including a fumble that set up Mannion's 23-yard touchdown pass to Woods, and an interception that set up a 31-yard field goal by Owens.

Portland State fell to 2-31 against NCAA Division I FBS programs, including a 0-13 mark against Pac-12 teams and a 0-4 record against Oregon State.

Next week, the Beavers play at Hawaii, while the Vikings are home against NCAA Division II Eastern Oregon.