1. Preheat grill to medium-high heat.
2. Cut zucchini and yellow squash lengthwise into 1/4-inch-thick slices; coat squashes, bell peppers, and onion with cooking spray. Place vegetables on grill rack coated with cooking spray; grill 3 minutes on each side or until well browned. Remove vegetables to a cutting board; let cool. Chop bell peppers and onion into bite-sized pieces; place in a large bowl.
3. While vegetables cook, bring 1 cup water to a boil in a medium saucepan; gradually stir in couscous. Remove from heat; cover and let stand 5 minutes. Fluff with a fork.
4. Add couscous, tomatoes, and next 7 ingredients to vegetable mixture; toss well. Sprinkle each serving with cheese.
Young Chefs can:
Drain and rinse beans in strainer
Older Chefs can:
Halve tomatoes with adult supervision
Crumble and sprinkle cheese