Start by preheating the oven to 350 degrees. While the oven is heating, put together the meatloaf.
In a large bowl, mash together the bread and milk until it forms a paste.
To the paste, add the ground turkey, Italian sausage, eggs, breadcrumbs, grated parmesan cheese, Italian seasoning, onion powder, granulated garlic, salt, pepper, ½ cup of the shredded mozzarella cheese, and 1/2 cup of the marinara sauce.
Mix all of the ingredients, using your hands, until everything is evenly distributed.
Line a large rimmed baking sheet with foil and then spray with cooking spray. Place the mixture onto the pan and form it into a loaf shape.
Spread the remaining marinara sauce over the meatloaf.
Put the meatloaf into a preheated oven and bake the meatloaf for 60 - 70 minutes. When the internal temperature registers 160 then the meatloaf is done.
Remove the meatloaf from the oven and then set the oven to broil.
Sprinkle the rest of the shredded cheese over the top and broil for 2-3 minutes, or until the cheese melts.
Remove meatloaf from the oven, let it sit for about 5 minutes, and then cut into thick slices and serve.