Start with preheating the oven to 350 degrees.
While the oven is heating, work on the onion and mushrooms. If you're using other vegetables, this is the time you'll cook those too. Heat the olive oil in a large skillet over medium-high heat. Add the onions and mushrooms and sauté until the onions are translucent and the mushrooms are soft. Season with salt and pepper. Drain extra liquid from the vegetables if needed and then place into a small bowl and set aside to cool.
While the vegetables cool, mix the meatloaf.
Combine the bread and milk in a large bowl until it forms a paste. Then add the eggs to the paste and mix until combined.
To the mixing bowl, add in the ground turkey, 1/2 cup of the pizza sauce, pepperoni (make sure to save 6- 8 slices for the top of the meatloaf), 1 cup mozzarella cheese, Italian seasoning, garlic powder, onion powder, salt, Worcestershire sauce, and romano cheese. Lightly mix all the ingredients.
Add vegetables and mix again until evenly distributed in the meatloaf mixture.
Pour the meatloaf mixture onto a large rimmed baking sheet sprayed with cooking spray. You can also use a meatloaf pan.
Then spread 1/2 cup of the pizza sauce over the top.
Place it into the oven and cook for 1 hour. The internal temperature should be 165 degrees when it's done cooking.
Remove the meatloaf from the oven and set the oven to broil.
Sprinkle the rest of the mozzarella cheese on the meatloaf, and then place 6-8 slices of pepperoni over the cheese.
Broil for 2-3 minutes or until the cheese is melted and the pepperoni gets crisp. Keep your eye on the meatloaf because it can burn quickly.
Remove from the oven and sit for about 3-5 minutes to seal in all juices.
Cut into eight slices and serve hot.