PREPARATION:

1. Preheat oven to 350°F. Place garlic in ovenproof dish. Spray garlic with cooking spray. Cover with foil; bake 30 to 35 minutes or until garlic is very soft and golden brown. Place garlic, vinegar, lemon juice, olive oil and black pepper in food processor; cover and process, using on-off pulses, until smooth. Set aside. Slice top from bread loaf. Hollow out loaf, leaving 1/2-inch-thick shell. (Reserve bread for another use, if desired.)
2. Spray cold grid of grill with cooking spray. Prepare grill for direct grilling. Brush eggplant, squash, onion and bell pepper with garlic mixture. Arrange vegetables on grid over medium coals. Grill 10 to 12 minutes or until vegetables are crisp-tender, turning once. Separate onion slices into rings. Layer half of eggplant, squash, onion, bell pepper, cheese and spinach in hollowed bread, pressing gently after each layer. Repeat layers with remaining vegetables, cheese and spinach. Replace bread top and serve immediately or cover with plastic wrap and refrigerate up to 4 hours. Cut into wedges before serving.