Preheat oven to 350°F (175°C) and grease a 9x5 inch loaf pan.
Heat olive oil in a skillet over medium heat. Sauté the diced bell pepper and onion until softened, approximately 5-7 minutes. Add minced garlic and cook for an additional 60 seconds. Remove from heat and allow to cool slightly.
In a large mixing bowl, combine the ground beef, breadcrumbs, eggs, beef broth, Worcestershire sauce, salt, pepper, and the sautéed vegetable mixture. Mix by hand until just combined; do not overwork the meat.
Place half of the meat mixture into the prepared loaf pan, pressing down to create an even layer.
Place the provolone cheese slices over the meat, folding them as necessary to fit and keeping them away from the very edges of the pan.
Top with the remaining meat mixture, pressing down firmly and sealing the edges to ensure the cheese is fully encased.
Bake for 50-55 minutes, or until the internal temperature reaches 160°F (71°C).
Sprinkle the shredded mozzarella over the top of the loaf and return to the oven for 5 minutes, or until the cheese is melted and bubbly.
Allow the meatloaf to rest for 10 minutes before slicing and serving.