Preheat your oven to 375°F (190°C). Lightly grease a baking dish. This prevents the casserole from sticking during baking.

Heat olive oil in a large skillet over medium heat. Add ground beef and cook until browned. Break the meat into small pieces.

Add chopped onion and minced garlic to the skillet. Cook for three minutes until soft and fragrant.

Add taco seasoning, salt and pepper. Stir well so the beef absorbs all the spices.

Pour the tomato sauce into the skillet. Mix well and cook for three minutes until the sauce thickens slightly.

In a bowl, combine cream cheese and sour cream. Stir until smooth and creamy.

Add the creamy mixture into the skillet. Stir gently until everything blends into a rich and creamy taco filling.

Stir in diced bell peppers and black olives. Cook for two minutes to soften the vegetables slightly.

Pour the beef mixture into the prepared baking dish. Spread it evenly with a spoon.

Sprinkle shredded cheddar and mozzarella cheese evenly over the casserole.

Place the dish in the oven. Bake for 20–25 minutes until the cheese melts and becomes golden.

Remove from oven and sprinkle chopped green onions on top. Let the casserole cool slightly before serving.