Bake garlic bread according to package directions. Decrease temperature on oven to 350 degrees F. Coat a 9×13 baking dish with cooking spray and line the bottom of the pan with a single layer of the prepared garlic bread slices.
In a medium bowl, combine the cream cheese, mayo and Italian seasoning. Mix well and spread evenly over the tops of the garlic bread slices. Sprinkle 1 cup of mozzarella over the top, followed by the marinara sauce and meatballs (no need to thaw meatballs first).
Top with 1 cup of mozzarella and bake in the preheated oven for 30 minutes. Serve warm!