Jay Smith had six catches for 98 yards and TD, while Catlin Schneider and Connor Haas also had touchdowns through the air for Regina.
Michael Kiapway rushed for 124 yards on 24 carries for the Rams (2-1).
In the only other game in the CIS, McGill pounded Mount Allison 36-9.
At Edmonton, Curtis Dell was 17-for-32 passing for 206 yards and a touchdown for Alberta (0-3). He ran in another score, but also threw two interceptions.
The teams were tied 10-10 when Mueller hooked up with Smith on a 36-yard TD pass early in the fourth quarter.
Mueller ran in another score to make it 24-10 before tossing 20-yard touchdown strike to Schneider.
Dell scored on a one-yard run with 33 seconds left on the clock to round out the scoring.
Redmen 36, Mounties 9
At Montreal, Ryne Bondy threw three TDs as McGill (1-2) scored 25 points in the first quarter on the way to defeating Mount Allison (0-2).