Preheat your oven to 375°F (190°C).
In a large skillet, heat the olive oil over medium heat. Add the sliced onion and bell pepper, sautéing until they are softened, about 5 minutes.
Add the mushrooms to the skillet and continue cooking for another 5 minutes until they release their moisture and start to brown.
Push the vegetables to the side of the skillet. In the same skillet, add the ground beef. Break it apart with a spoon and cook until it’s browned, about 8-10 minutes. Drain any excess fat if necessary.
Mix the sautéed vegetables into the ground beef. Stir in the garlic powder, onion powder, salt, and pepper. Remove from heat.
In a mixing bowl, combine the softened cream cheese with half of the provolone and mozzarella cheese, mixing until well combined.
Grease the casserole dish, then layer half of the beef and veggie mixture on the bottom. Spread the cream cheese mixture evenly over this layer, then top with the remaining beef and veggie mixture.
Finish by sprinkling the remaining provolone and mozzarella cheese on top of the casserole.
Bake in the preheated oven for 25-30 minutes, until the cheese is bubbly and golden brown.
Remove from the oven and let it sit for a few minutes before slicing and serving.