Heat a skillet over medium-high heat and add the thinly sliced beef. Cook until browned, about 5-7 minutes.

In the same skillet, add the sliced green bell pepper and onion. Sauté for 3-4 minutes until softened.

Cut the French or Italian loaf lengthwise to create a pocket. Spoon in the beef and vegetable mixture, then top with shredded provolone cheese.

Mix melted butter with minced garlic (if desired) and brush over the stuffed loaf.

Preheat your oven to 375°F (190°C). Bake the loaf covered for 15 minutes, then uncover and bake for another 10-15 minutes.