Texas and Oklahoma, the top two seeds in the regional in Norman, Okla., had no trouble winning their first-round games Thursday as the NCAA softball national tournament got going Thursday at eight regional sites with six teams at each site.

Texas beat Army 4-0 as Cat Osterman and Amy Bradford combined on a one-hitter. Oklahoma followed with a 6-0 victory over Utah.

The Longhorns (49-11), who won the Big 12 regular-season and tournament titles, used a three-run fourth inning to take control. Army committed three of its five errors in the inning.

Osterman pitched no-hit ball through five innings, striking out 12.

Oklahoma (46-14) got two hits from each of its first four batters. After the Sooners scored an unearned run in the fourth inning, they added three in the fifth, two on a single by Erin Evans.

In the other first-round game Thursday in Norman, Lindsay Wilhelmson hit a three-run homer to lead Texas A&M to a 6-2 victory over Arkansas (32-27). The Aggies (39-16) will play Oklahoma on Friday.

Army (31-18-1) scored two runs in the sixth inning to eliminate Utah 2-0 in a late game Thursday.

At Iowa City, Nebraska and Oregon State won with pitching and Notre Dame did it with clutch hitting.

Lisa Mattison's two-run single in the bottom of the seventh inning gave Notre Dame a 3-2 victory over Iowa, which beat the Irish in a regional championship game last year to advance to the College World Series.

Nebraska's Peaches James and Leigh Ann Walker combined on a three-hitter in a 1-0 victory over Illinois-Chicago, while Oregon State's Crystal Draper and Monica Hoffman held Wisconsin to three hits, also in a 1-0 victory.

Notre Dame (43-15) and Oregon State (39-23) will meet in the second round of the double-elimination tournament Friday. Nebraska (46-12), the top-seeded team in the regional, will meet an opponent to be determined.

Iowa (35-19) took a 2-1 lead against Notre Dame in the top of the seventh on Kristin Johnson's run-scoring double. But the Irish rallied in their half of the inning against Kristi Hanks.

Andrea Loman and Jarrah Myers started the inning by drawing consecutive walks off Hanks, who did not walk anyone in the first six innings. Both runners advanced on Andria Bledsoe's bunt and Mattison followed with her game-winning hit to right-center.

Nebraska made a first-inning run stand up against Illinois-Chicago. Kim Ogee singled leading off, stole second and scored when Amanda Buchholz doubled down the left field line.

James struck out three with no walks in 3 1/3 innings. Walker relieved after Amber Stachura singled with one out and struck out two consecutive batters for her second save. That ran Walker's career strikeout total to 838, tying the school record.

Michelle Chariton scored Oregon State's run in the first inning when Shelley Prochaska hit a ball that bounced off the third base bag and rolled toward the OSU dugout.

Draper and Hoffman both struck out five, Draper giving up two hits while working the first 3 2/3 innings.