Preheat oven to 400 F. While the oven heats up, pour the entire bag of meatballs into a medium saucepan along with your preferred marinara or spaghetti sauce. For added flavor, feel free to enhance the sauce with garlic, onion powder, salt, and pepper to your liking. Heat the meatballs over medium heat, stirring occasionally to prevent sticking, until they are warmed through, which typically takes about 10 minutes. Once heated, remove the saucepan from the heat source.
Meanwhile, lightly spread each slice of bread with butter or brush them lightly with olive oil. Arrange the prepared bread slices on a sheet pan, ensuring they are evenly spaced. Even if you opt to leave the bread plain, the dish will still turn out wonderfully flavorful and delicious.
Arrange the meatballs and sauce evenly in the center of a 9x13 baking dish. Next, generously layer a mixture of mozzarella and Italian blend cheeses over the meatballs, ensuring they are fully covered. Finish by sprinkling a generous amount of Parmesan cheese on top to add a deliciously savory finish to the dish.
Transfer the prepared baking dish of meatballs and the sheet pan of bread slices into the preheated oven. Bake for approximately 25 minutes, or until the cheese is golden brown and bubbly, and the bread slices are lightly toasted. It's essential to monitor the bread closely, as oven temperatures may vary, ensuring it reaches the perfect level of crispness without burning.
Once baked, carefully take the dish out of the oven. Arrange the toasted bread slices around the meatballs in the pan. This adds a nice touch to the presentation and gives a variety of textures. Serve and enjoy this tasty Italian Cheesy Bake, perfect for 6 to 8 servings. It's easy to make for larger gatherings too.