Preheat oven to 375°F (190°C).

In a large skillet, cook chopped bacon over medium heat until crisp. Remove bacon and set aside, leaving about 1 tablespoon of bacon fat in the pan.

Add olive oil if needed, then cook chopped onion in the skillet until soft, about 3 minutes. Add garlic and cook for 30 seconds.

Add ground beef, salt, pepper, and oregano. Cook and stir until beef is browned and cooked through. Drain excess fat if needed.

Stir in drained diced tomatoes and corn or bell pepper if using. Cook for 2 minutes to warm.

Turn off the heat. Stir in sour cream and half of the cheddar and mozzarella. Mix well.

Pour the beef mix into a baking dish. Sprinkle the reserved crispy bacon on top and then add the rest of the cheddar and mozzarella.

Bake in the oven for 15 to 20 minutes, until cheese is bubbly and golden.

Let rest for 5 minutes before serving.