Creating Overnight Breakfast Casserole is a breeze when you follow these simple steps:

1. Prepare the Bread: Tear the loaf of bread into bite-sized pieces and place them in a large mixing bowl.
2. Cook the Meat: In a skillet over medium heat, cook the breakfast sausage or bacon until browned. Drain excess fat and set aside.
3. Sauté Vegetables: In the same skillet, add diced onions and bell peppers. Sauté until soft, about 5 minutes.
4. Mix the Egg Mixture: In a separate bowl, whisk together the eggs, milk, garlic powder, salt, black pepper, and dried mustard until well combined.
5. Combine Ingredients: Add the cooked sausage, sautéed vegetables, and shredded cheese to the bread pieces. Pour the egg mixture over everything, ensuring even coverage.
6. Refrigerate: Cover the bowl with plastic wrap and refrigerate overnight (or at least for 4 hours) to allow the bread to absorb the egg mixture.
7. Preheat the Oven: In the morning, preheat your oven to 350°F (175°C).
8. Bake: Remove the casserole from the fridge and uncover. Bake in the preheated oven for 45-50 minutes, or until the top is golden brown and the center is set.
9. Cool and Serve: Allow the casserole to cool for about 5-10 minutes before slicing. Garnish with fresh herbs if desired.

These steps will guide you in creating this incredible casserole effortlessly.