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

1. Preheat Oven: Preheat your oven to 375°F (190°C).
2. Cook Sausage: In a large skillet over medium heat, add the Italian sausage. Cook until browned, breaking it into small pieces as it cooks. Drain excess fat if necessary.
3. Sauté Vegetables: In the same skillet, add olive oil. Once hot, add sliced onions and bell peppers. Sauté until they are tender, about 5-7 minutes.
4. Add Garlic: Stir in minced garlic and cook for an additional minute until fragrant.
5. Combine Ingredients: Add the browned sausage back to the skillet. Then, stir in the diced tomatoes, oregano, basil, red pepper flakes, salt, and pepper. Let this mixture simmer for about 5 minutes.
6. Mix in Pasta: In a large mixing bowl, combine the sautéed sausage and pepper mixture with the cooked pasta. Mix well to ensure everything is evenly coated.
7. Transfer to Baking Dish: Pour the mixture into a greased 9×13 inch baking dish. Spread it out evenly.
8. Add Cheese: Sprinkle shredded mozzarella cheese generously over the top.
9. Bake: Place the baking dish in the preheated oven and bake for 25-30 minutes, or until the cheese is melted and bubbly.
10. Garnish: Remove from the oven and let it cool for a few minutes. Garnish with fresh basil leaves before serving.

By following these simple steps, you’ll create a delicious and comforting Italian Sausage & Pepper Casserole that will wow your family and friends.