Preheat broiler. Microwave meatballs, covered, on high until heated through, 4-6 minutes. Meanwhile, place bread on an ungreased baking sheet; brush one side of bread with oil. Broil 4-6 in. from heat until golden brown, 1-2 minutes. Rub bread with cut surface of garlic; discard garlic. Tear bread into bite-sized pieces; transfer to a greased 11x7-in. baking dish. Reduce oven setting to 350°., Add pasta sauce, 1/4 cup mozzarella cheese and 1/4 cup Parmesan cheese to meatballs; toss to combine. Pour mixture over bread pieces; sprinkle with remaining cheeses. Bake, uncovered, until cheeses are melted, 15-18 minutes.