Preheat your oven to 350°F (175°C). Line a baking sheet with parchment paper or lightly grease a loaf pan.
2. Sauté the Vegetables
In a skillet, heat the olive oil over medium heat. Add the onions, bell peppers, and mushrooms (if using) and sauté for about 5-6 minutes until softened.
Add the minced garlic and cook for another 1-2 minutes until fragrant. Remove from heat and let cool slightly.
3. Prepare the Meatloaf Mixture
In a large mixing bowl, combine the ground beef, sautéed vegetables, shredded cheese, breadcrumbs, eggs, milk, Worcestershire sauce, garlic powder, onion powder, salt, and pepper.
Mix everything together with your hands or a spatula until well combined, but avoid overmixing to keep the meatloaf tender.
4. Form the Meatloaf
Shape the meat mixture into a loaf and place it on the prepared baking sheet, or press it into a greased loaf pan.
5. Bake
Bake the meatloaf in the preheated oven for 45-50 minutes, or until the internal temperature reaches 160°F (71°C).
6. Add the Cheese Topping
In the last 10 minutes of baking, sprinkle the remaining shredded provolone or mozzarella over the top of the meatloaf. You can also add additional sautéed onions and peppers as a garnish on top if desired.
Return the meatloaf to the oven and bake until the cheese is melted and bubbly.
7. Serve
Let the meatloaf rest for about 5 minutes before slicing. Serve hot with your favorite sides like mashed potatoes, roasted vegetables, or a salad.
