1. To prepare pesto, drop garlic through food chute with food processor on; process until minced. Add walnuts and basil; process until finely ground. Add cheese and next 3 ingredients (through water); process until smooth. Transfer to a small bowl; cover and chill.
2. To prepare salad, preheat grill to medium-high heat.
3. Place eggplant and onion on grill rack coated with cooking spray; cover and grill 6 to 8 minutes or until tender. Remove from grill.
4. Place zucchini and yellow squash on grill rack; cover and grill 4 to 6 minutes or until tender. Remove from grill.
5. Thread tomatoes evenly onto skewers; coat with cooking spray. Place skewers on grill rack; cover and grill 5 to 7 minutes or until tender. Remove tomatoes from skewers.
6. Arrange vegetables, tomatoes, and cheese on a large platter; drizzle 1/2 cup pesto over salad, and sprinkle with salt. Serve with remaining pesto.