Houston jumped on BYU in the first inning, batting through the order as it scored eight runs on four hits and two errors.
BYU cut the deficit in half in the bottom of the first with walks by Ailana Agbayani and Maddie Bejarano before a three-run homer from Violet Zavodnik to left field. It tacked on one more as a Keila Kamoku single scored Lily Owens, making in 8-4, Houston.
Houston added another run in the second on two singles to left, a wild pitch, walk to lead 9-4.
Zavodnik and Owens both singled in the bottom of the third, with Zavodnik scoring on a Houston throwing error after a line out for a 9-5 score.
BYU exploded for seven runs in the fourth to tie and take the lead, its first of the game. Hailey Morrow led off with a full-count home run to left center before BYU scored on four consecutive at-bats: a Huntyr Ava single, Owens double, Maddie Udall single and no doubter long bomb by Keila Kamoku, a three-run shot that made it 12-9, BYU.
Houston got two runs back in the top of the fifth inning with two singles, two ground outs and a double that cut the BYU lead to one, at 12-11.
Houston homered in the seventh to retake the lead, going in front 13-12, but Agbayani answered back with a two out solo shot to even things up at 13, sending the game into extras.
Both teams had their chances in the eighth, including a two-on no-out opportunity for BYU, but neither could scratch the winning run across.
Houston took control in the top of the ninth on three singles and a hit by pitch, gaining a 15-13 advantage.
BYU loaded the bases in the bottom of the ninth after Taryn Lennon and Zavodnik walks, and a Tristen Turlington single. With Ava up to bat and a 2-0 count, the first baseman smacked a line drive over the left field wall, walking it off for BYU with a grand slam, its seventh of the season, sealing the extra inning victory and its first Big 12 series win.
On Deck
BYU will remain at home to face Utah Tech in a midweek game on Tuesday, April 2 at 5 p.m. MDT before heading out to Orlando for a three-game series at UCF.