Heat oven to 375°F; grease a 9-by-13-inch dish.

Toss bread with olive oil and Italian seasoning; spread in dish.

Warm meatballs in marinara, following package directions if needed.

Spoon meatballs and sauce over bread; add both cheeses.

Cover with foil; bake 20 minutes. Uncover; bake 10 more minutes until cheese melts and edges crisp.