Brandon Rutley and George Johnson also scored touchdowns for the Alouettes while Boris Bede added two field goals and a punt single before a sparse crowd announced as at Percival Molson Stadium.
Brett Maher kicked a field goal for Ottawa and another two points came from a safety.
The Alouettes dressed their first team while Ottawa went with second and third stringers and it showed as Montreal took a 29-0 halftime lead.
The opening kickoff was fumbled by Sharkir Bell and recovered by Bede, who turned it into a field goal at 1:44.
Durant hit Underwood with a 28-yard touchdown pass and, on the next drive, found Cunningham for a 55-yard TD. A two-point convert attempt failed.
A John Bowman fumble recovery led to a 40-yard Bede kick 5:44 into the second quarter. Rutley ran one in the from the six at 12:35 and Bede added another boot from 37 yards as the half ended.
Armageddon Draughn picked off a Vernon Adams pass at the Alouettes 51 in the opening minute of the second half but the Redblacks couldn’t turn it into points. Instead, Montreal marched back and Johnson nabbed a four-yard TD pass from Vernon Adams. Johnson also caught the two-point convert.
The Redblacks got on the board 10:41 into the third when Maher kicked a 23-yard field goal after Kevin Brown picked off a Matt Shiltz pass on the Montreal 22.
Ottawa started Ryan Lindley at quarterback, followed by Austin Trainor. Danny Colins took over midway through the third.
Durant played only the first quarter for Montreal. Jacory Harris also played in the fourth.