Cut zucchini and squash lengthwise into 1/4-inch-thick slices. Place zucchini, squash, bell peppers, and onion on a grill rack coated with cooking spray; grill 3 minutes on each side or until well browned. Remove vegetables to a cutting board; cool. Chop vegetables into bite-sized pieces; place in a large bowl.
Bring water to a boil in a medium saucepan. Stir in couscous and the next 5 ingredients (through cinnamon). Cover, remove from heat, and let stand 5 minutes. Fluff with a fork.
Add couscous, tomatoes, and remaining ingredients except cheese to vegetable mixture; toss well. Sprinkle each serving with cheese.