EaterBob sure hit the highlights (I'm still trying to figure out LaSalle Drive-In, though) leaving me clutching at straws...
Hows about Station des Sports on St. Catherine.
La Campagnola in LaSalle (about 2km from LaSalle Drive-In) - call ahead, they book solid.
Barfly on St. Laurent (well, perhaps not exactly a terrace - it was described by a customer as "zen garden gone to shit").
Portuguese Brasa on Duluth.
La Gargotte on Place d'Youville has a terrace in the park across the street (perhaps 30 capacity...).
Magnans on St. Patrick.
El Meson on St. Joseph in Lachine (nice lighting on the sumacs on a summer night. Squint and you can imagine being in Mexico).
Irish Embassy on Bishop.
Various on Crescent.
If you hang out in the parking lot of the Lasalle Drive-In , but on the side near (actually almost on top of) the river and squint slightly (because of the sun) it is a far better terrasse than you can imagine... Just make sure that despite your squinting, you don't fall in the river.
It also helps immensely if you're eating a Peter's Special and drinking beer out of a king can in a paper bag.
I'd also agree about the "zen garden gone to shit," and Na Brasa on Duluth. Both are very nice places with their own charms.
But I'd draw the line at Magnan's parking lot (aka the terrasse) it can't hold a candle to the Lasalle Drive-In or Benelux. I'd suggest the Capri if you really feel the need to eat and/or drink in traffic in Point Saint Charles. The food is better, the beer is cheaper, and the clientele is much more entertaining.
I listed Magnans simply because it met the criteria (hold at least 80 people), but similar to the places on Crescent (except Ziggy's, but they have no terrace) I try my best to avoid. I understand the appeal to many people, but I'm (and seemingly you) ain't one of them...
Capri is good, no doubt, but their terrace is what? 4 tables outside? Although I haven't been going to Capris all my life, I do remember it pre-Bourdain. It changed alot since then and to me, not necessarily for the better. I'm afraid its becoming just another gentrified establishment, like bar des Courcelles et al....but thats another thread.
One of Mrs. Porker's cousins once took Lasalle Drive-In literally and drove into the river. It was either late at night or early in the morning, depending, many years ago. No injuries, but he later said all he remembered was squinting, trying to stay on the road.
il cortile on sherbrooke west has nice patio in back and lemeac has terrace on side of restaurant. Jardin Panos also has terrace in back.. Apollo has taken over les eclusiers so when la cabane finishes its sugar shack season they will I presume reopen their terrace which is right on the locks across from silos in old montreal
Saint Sulpice on Saint Denis, Saint Ciboire onSaint Denis, Diablos on Saint Denis.
Benelux on Sherbrooke, Fino's on Sherbrooke,
Club Espagnol on Saint Laurent, Vice Versa on Saint Laurent. Le Frappe on Saint Laurent.
Espace La Fontaine in Parc Lafontaine, El Messon in Lachine, Le Pavillion on Mount Royal, Le Castillion at the Hotel Bonaventure, Cinematheque Quebecoise on de Maisonneuve, Les Accords on Notre Dame, Jardin Nelson on Place Jacques Cartier, Htel Nelligan on Saint Paul, Hotel Place d'Armes on Saint Jacques, Le Sinclair on Saint Sulpice, Club Chasse et Peche on Saint Claude, Lasalle Drive-In on Lasalle Blvd., Le Valois on Ontario.
And I'm certain with a little bit of research more can be found.