Well, you'd be surprised how many good restaurants put out terasses during the summer, and how many offer brunch. For example, you can enjoy brunch at M sur Masson, or at Lemeac.
If you're looking for a nice terasse, I enjoy the one at Croissanterie Figaro (more european type breakfast), or accross the street at Rumi. I also had a nice brunch recently at La petite Ardoise. Food is ok, not great, but beautiful patio in the back.
It would help if you specified an area, otherwise, the list can be quite long.
5198 Rue Hutchison, Outremont, QC H2V4A9, CA