In a large bowl, toss bread with 1/3 cup olive oil, salt, pepper, and garlic. Lay bread on a baking tray, and toast in the preheated oven until golden, about 5 to 10 minutes; allow to cool slightly.
While the bread is in the oven, whisk together 1/4 cup of olive oil and balsamic vinegar. Gently toss together the bread, tomatoes, onion, basil, olives, and mozzarella cheese. Toss with the vinaigrette and let stand for 20 minutes before serving.