Heat gas or charcoal grill. Spray bread slices with cooking spray; set aside.
Spray bell pepper, tomatoes, zucchini and onion with cooking spray. Carefully brush oil on grill rack. Place vegetables on grill over medium heat. Cover grill; cook 12 to 15 minutes, turning twice, until vegetables are slightly charred. Add bread slices to grill for last 4 to 6 minutes of cooking time, turning once, until toasted.
Cut vegetables into large chunks. Cut bread into 1-inch cubes. In large bowl, toss vegetables, bread cubes and capers. In small bowl, mix dressing and lemon juice; pour over vegetable mixture and toss well. Sprinkle with pepper and basil.