Preheat oven to 400°F.
Cook ground beef in a skillet over medium heat for 6–8 minutes, breaking it apart.
Add onion, bell pepper, and mushrooms.
Cook for 4–5 minutes, until vegetables soften.
Drain excess grease if needed.
Stir in Italian seasoning, garlic powder, salt, pepper, and marinara.
Divide mixture into 4 oven-safe bowls or a small baking dish.
Sprinkle mozzarella over the top.
Add olives and crushed red pepper if using.
Bake for 10–12 minutes, until cheese is melted and bubbly.
Let cool for a few minutes before serving.
For meal prep, store the cooked beef and sauce mixture in containers, then add cheese before reheating so it melts fresh.
