Preheat oven to 375°F (190°C) and line a baking sheet with parchment paper.
Heat olive oil in a skillet over medium-high heat; sauté the green pepper, onion, and mushrooms for 6 minutes until softened and moisture has reduced.
In a large mixing bowl, combine the ground beef, sautéed vegetables, breadcrumbs, eggs, Worcestershire sauce, garlic powder, salt, and pepper.
Mix by hand until just combined; do not overwork the meat.
Form the mixture into a 9x5-inch loaf shape on the prepared baking sheet.
Bake for 45 minutes.
Remove from oven and layer the provolone cheese slices across the top of the loaf, overlapping as needed.
Return to the oven and bake for an additional 15 minutes, or until the internal temperature reaches 160°F (71°C).
Allow the meatloaf to rest for 10 minutes before slicing to ensure the structure sets.