In a large bowl, combine the ground beef, breadcrumbs, chopped onion, minced garlic, egg, Worcestershire sauce, Italian seasoning, salt, and pepper. Mix until well combined.
Transfer the meat mixture to an 8x8 inch baking dish, pressing it evenly across the bottom. Bake in the preheated oven for 25 minutes.
After 25 minutes, remove the casserole from the oven. Spread the marinara sauce evenly over the cooked meatloaf layer. Sprinkle the diced bell pepper and corn kernels over the sauce.
Top everything with the shredded cheddar cheese, ensuring it's evenly distributed.
Return the casserole to the oven and bake for an additional 15-20 minutes, or until the cheese is melted and bubbly.
Remove from the oven and let it cool for a few minutes. Garnish with fresh chopped parsley before serving.
Notes
Let the casserole cool for a few minutes before serving for better slicing.