In 10- to 12-inch skillet, heat 4 tablespoons of the oil over medium heat. Arrange bread pieces in single layer in skillet (you will have to do a few batches). Cook until golden; turn and cook again. Repeat with remaining bread. Remove from skillet; cool.
In same skillet, heat remaining tablespoon oil over medium heat. Add bell peppers, zucchini and onion; cook 3 to 6 minutes or until tender. Cool.
In very large bowl, place bread, cooked vegetables, tomatoes and dressing; add salt and pepper to taste. Toss; serve immediately.