Preheat oven to 350 degrees then coat inside of an 8" square casserole dish with olive oil. Cut bread into 1" cubes then arrange in an even layer in bottom of casserole dish, pressing into the pan to create a firm layer.
Place cream cheese in a small microwave-safe bowl then heat for about 30 seconds, until very soft. Remove from microwave, stir until smooth. Add garlic powder, oregano, basil, salt and pepper then stir to combine. Spread cream cheese over bread using the back of a spoon to coat evenly.
Sprinkle ½ cup of shredded mozzarella over the cream cheese layer, reserving the remaining cheese for topping. Distribute meatballs evenly across top of the bread and cheese layer then cover with marinara sauce. Cover tightly with aluminum foil.
Bake 40–45 minutes, until the sauce is hot and bubbly and meatballs are heated through. Remove foil, sprinkle remaining mozzarella cheese over the top then return to oven. Bake, uncovered, for an additional 5–7 minutes—just long enough to melt the cheese.
Notes
Cutting the bread before you place it in the casserole dish will make serving so much easier!