Head Coach Franco Smith also welcomes back four additional Scotland internationals into the starting XV, strengthening a squad that finished the pool stage with a perfect 20 points from 20 to secure second seeding for the knockout rounds.
Victory over the South African visitors would guarantee Glasgow a home quarter-final.
Zander Fagerson returns to the lineup for the first time since the Guinness Six Nations, joining Patrick Schickerling and Gregor Hiddleston in the front row.
In the second row, Alex Samuel partners Max Williamson, who scored one of Glasgow's five tries in last weekend's win over Benetton.
The back row sees Jack Dempsey start at number eight following his nomination for the 2025/26 Investec Player of the Year award, alongside returning internationals Matt Fagerson and Rory Darge.
At scrum-half, George Horne comes back into the starting XV after being rested last weekend, with Dan Lancaster continuing at fly-half.
Stafford McDowall, who captained the side to victory over Leinster a fortnight ago, starts at outside centre alongside Sione Tuipulotu.
Steyn resumes leadership duties from the wing, having beaten more defenders than any other Glasgow player during the pool stage. Ollie Smith and Josh McKay complete the back three.
Among the replacements, a 6-2 split sees Ben Afshar and Adam Hastings cover the backs, while Sam Talakai - fresh from signing a new contract - is joined by Seb Stephen and Jamie Bhatti as front-row cover.
Jare Oguntibeju is named at number 19, with Euan Ferrie and Angus Fraser completing the bench.
Speaking after selection, Smith said: "We are fully aware of the challenge that the Bulls will bring tomorrow evening; they have a squad filled with international-calibre talent and have a strong track record of competing in knockout fixtures.
"We know that we must front up to face what the Bulls throw at us, and training this week has been highly competitive with everyone driving each other forward.
"The atmosphere at Scotstoun in the Champions Cup this season has been on another level, and we know that the Warrior Nation will be in full voice behind us once more tomorrow evening."
15 Josh McKay
14 Kyle Steyn (Captain)
13 Stafford McDowall
12 Sione Tuipulotu
11 Ollie Smith
10 Dan Lancaster
9 George Horne
1 Patrick Schickerling
2 Gregor Hiddleston
3 Zander Fagerson
4 Max Williamson
5 Alex Samuel
6 Matt Fagerson
7 Rory Darge
8 Jack Dempsey
Substitutes
16 Seb Stephen
17 Jamie Bhatti
18 Sam Talakai
19 Jare Oguntibeju
20 Euan Ferrie
21 Angus Fraser
22 Ben Afshar
23 Adam Hastings
Unavailable:
Gregor Brown (hamstring), Alex Craig (foot), Scott Cummings (calf), Jamie Dobie (shoulder), Nathan McBeth (ankle), Kyle Rowe (hip), Charlie Savala (knee), Tavi Tuipulotu (knee)