Tennessee (7-1) shot 46.8 percent from the floor and held the Longhorns to 34.3 shooting in winning for the fourth straight year against Texas.
Ariel Massengale and Taber Spani had 15 points apiece for Tennessee and Cierra Burdick and Bashaara Graves scored 14 each. Graves also had 10 rebounds. Jasmine Jones added 10 points and nine rebounds for the Lady Vols.
Simmons, who is from Cibolo, Texas, about 45 minutes from Austin, showed the nerves associated with playing before her friends and family in the opening 10 minutes. But she settled down and spurred the Lady Vols at the end of the first half and the beginning of the second.
Chassidy Fussell led the Longhorns (6-2) with 31 points. Fussell, a native of Troy, Tenn., missed the last two games with a head injury. She was 10 of 10 from the free-throw line on Sunday and recorded the third 30-plus performance of her career and the first for a Longhorn this season.
Nneka Enemkpali was the only other Longhorn player to score in double figures with 15 points and eight rebounds. Texas had 17 turnovers to Tennessee's 12.
Texas shot 25 percent and trailed 45-27 at halftime. The Longhorns cut the Tennessee lead to 78-68 on Fussell's 3-pointer with 6:57 to play before the Lady Vols finished the game with a 16-7 run.
Tennessee leads the series against Texas 22-12 and the Lady Vols are 52-17 all-time against Big 12 teams. The victory was Tennessee's third win this season against a ranked opponent on the road. Tennessee is now 4-0 against ranked teams in 2012.
This was the Lady Vols' first game in two weeks and was Tennessee's seventh consecutive win after a season-opening loss to Chattanooga.
Texas has lost two of three after starting the season 4-0.
Spani came off the bench to lead the Lady Vols in the first half, scoring all 15 of her points helped by a 3-for-3 showing from the behind the 3-point line.