Preheat your oven to 350°F (175°C). Grease your loaf pan with cooking spray or oil.

Sauté chopped onions, bell peppers, and mushrooms in a skillet over medium heat for 5-7 minutes until soft.

In a mixing bowl, combine the sautéed vegetables with ground beef, Worcestershire sauce, breadcrumbs, and eggs. Mix gently.

Transfer the mixture into the greased loaf pan, shape into a loaf, and create a well in the center.

Fill the well with shredded provolone or American cheese.

Bake in the preheated oven for about 50 minutes or until the internal temperature reaches 160°F (70°C).

Let the meatloaf rest for 10 minutes before slicing.