Preheat your oven to 375°F (190°C).

In a skillet, heat olive oil over medium heat and sauté diced bell pepper and onion for 5 minutes, until softened and fragrant. Remove from heat and set aside.

In a large bowl, combine ground beef, breadcrumbs, egg, milk, Worcestershire sauce, garlic powder, salt, and black pepper. Mix gently until fully incorporated, being careful not to overmix.

Press half of the meat mixture into a greased loaf pan. Layer 4 slices of provolone over the meat, then spread the sautéed peppers and onions evenly. Top with the remaining meat mixture, pressing gently to seal the edges.

Bake the loaf for 45-50 minutes. In the last 5 minutes, arrange the remaining 4 provolone slices on top and bake until melted and slightly golden.

Let the meatloaf rest for 5-10 minutes before slicing. Garnish with parsley if desired and serve warm.