Griner's record 15th dunk was the first of several plays that drew big roars from the crowd with the game well in hand in the second half. The Lady Bears (33-1), the overall No. 1 seed, won their 31st straight game since an early-season loss to Stanford, another top seed.
Odyssey Sims had 12 points and 10 assists, and Destiny Williams had nine points and 10 rebounds off the bench.
Gabrielle Scott led Prairie View with 14 points off the bench. The Lady Panthers (17-15) lost as a No. 16 seed for the third year in a row. Two of them were against Baylor in Waco, and the other was to Connecticut.
Baylor's lead was just 22-15 midway through the first half when coach Kim Mulkey called timeout and stared down Kimetria Hayden for letting Gabrielle Scott hit a 3-pointer that gave Prairie View five points in just 35 seconds.
The Lady Bears scored the next five points coming out of the timeout to start a 17-4 run that put them ahead 39-19 late in the first half. Griner, who had her 61st career double-double, scored 10 in the spurt and had 20 in the first half.
Griner's latest dunk - she had two in the NCAA tournament last year - came right after Prairie View had scored to make it 49-26. Sims found Griner alone under the basket and threw a pass three-quarters the length of the floor. Griner caught it, turned under the basket and dunked with one hand on the other side of the rim.
A few minutes after Griner's dunk, Prairie View's Tanisha Lacey took the ball away from Griner and tried to shoot over her. Griner didn't even let the shot get out of Lacey's hand, stuffing it out of bounds. With the crowd still wildly cheering the block, Sims got a steal and threw the ball ahead to Hayden, who converted a three-point play for Baylor's first 30-point lead.
Sims pleased the crowd again a few minutes later when she almost kicked the ball out of bounds on a fast break, but saved it to Brooklyn Pope. Sims was waiting for a return pass under the basket, and the layup put Baylor ahead 62-28.
The finishing touch came from Sims, too - a 3-pointer for a 70-30 lead with 9:07 left in the game.
Playing for the first time in nearly two weeks, Baylor let the Lady Panthers stay close in the first few minutes, thanks in part to a stretch of a minute and a half when the Lady Bears didn't even get off a shot. Prairie View got a steal and had three straight offensive rebounds before Kiara Etienne hit a 3-pointer to give the Lady Panthers their only lead at 6-5.
Prairie View qualified for the tournament by beating Mississippi Valley State in four overtimes in the Southwestern Athletic Conference championship game.
Leading scorer Latia Williams started quickly for Prairie View, but was just 2 of 10 from the field in the second half and finished with 10 points.