After falling down 2-0 early, the Sooners rattled off 10 unanswered runs to secure their fifth run rule in seven postseason games.
Pitcher Keilani Ricketts got the onslaught started with an RBI double into the right field corner.
But that was just the beginning of a six-run third inning.
Right fielder Callie Parsons, who finished 2-for-3 with three RBI and a run scored, picked up a pair with her single up the middle that put OU on top 3-2.
"Yeah, she [Kim Bruins] came out and threw two balls on me and went back to back low outside, and sitting up there with the 2 2 count I knew that the girls in front of me did everything they could to get on base and did their job," Parsons said. "So I had to do everything I needed to do to fight and find my way on. The 3 2 count, I was just trying to see the ball into the zone and get a good hack on it."
She certainly did, and it set the table for even more.
Left fielder Brianna Turang, one of the most un-talked about players considering her plus-.400 average, put down a beauty of a bunt that turned into a single and bases-clearing play by virtue of an error.
That made it 6-3 OU.
"I think because there were runners in scoring position, I saw they were a little bit back," Turang said. "So, my goal was kind of to put it in between to where they kind of didn't know who was going to get the ball. It went a little bit over. I didn't expect it. But I just tried to run my butt off to get to first and just kind of see what happens, just use my speed to maybe put pressure on the defense."
Ricketts, who settled down after allowing those two early runs, got plenty more offense to support her.
Casey polished off their third victory of the season over the Longhorns with an RBI singlie to right center.
"That was fun," said OU head coach Patty Gasso. "We enjoyed it very much, not necessarily because of the outcome of the amount of the score, because we respect Texas like nobody else. We were really feeling that this was going to be a major battle. We knew it right from the start.
"But what was fun is to see every single one of these players participate in the win, whether they're starters or not. Everybody had a hand in helping create a rally or drive in runs or make big plays. Everybody had a part in it, and I was extremely proud to see this team fight. Early on, not getting panicked by the fact that Texas came out and scored early and scored two early. We just kind of took our time and were patient and created some momentum and tried to stay aggressive. It seemed to work out really well."
Any other result, and OU will be headed to the championship once again to get a crack at what it fell short of last year.
"It allows us to get a little extra rest, allows us to do our research and homework as to who we're going to face next," Gasso said. "For two teams and being us and Tennessee, it's really a tremendous advantage."
OU next takes the field at 8:30 p.m. CT Sunday.