Creating Italian Sausage & Pepper Casserole is simple if you follow these easy steps:

1. Preheat the Oven: Preheat your oven to 375°F (190°C).
2. Cook the Sausage: In a large skillet over medium heat, add the Italian sausage. Cook until browned, breaking it into smaller pieces as it cooks. Remove the sausage and set it aside.
3. Sauté Vegetables: In the same skillet, add olive oil. Sauté the sliced onion and bell peppers for about 5 minutes until they begin to soften. Add minced garlic and cook for an additional minute.
4. Combine Ingredients: Return the cooked sausage to the skillet. Stir in the diced tomatoes, tomato sauce, Italian seasoning, salt, and black pepper. Mix well to combine.
5. Transfer to Baking Dish: Pour the sausage and pepper mixture into a baking dish, spreading it evenly.
6. Add Cheese: Sprinkle shredded mozzarella cheese on top of the mixture.
7. Bake: Place the casserole in the preheated oven and bake for 30 minutes or until the cheese is bubbly and golden.
8. Garnish: Remove from the oven and let it cool for a few minutes. Garnish with fresh basil leaves if desired before serving.

These steps will guide you in creating a delicious Italian Sausage & Pepper Casserole that your family will adore!