Preheat your oven to 350°F. Lightly grease a 9x13 baking dish to prevent sticking.

In a skillet over medium-high heat, add the sausage, onion, and red pepper. Cook until the sausage is no longer pink and the vegetables have softened, about 5-7 minutes. Drain the excess grease from the skillet.

Stir in the spinach and cook for another 1-2 minutes. Remove the skillet from heat and let the mixture cool slightly.

In a large bowl, combine the remaining ingredients. Mix everything together until well combined.

Stir the sausage mixture into the bowl with the egg mixture. Pour everything into the prepared baking dish and top with more cheese.

You can either bake the casserole immediately or refrigerate it to bake the next day. Cover it tightly if you choose to refrigerate.

Bake uncovered for 25-30 minutes. Look for the eggs to be set and the cheese to be bubbly and slightly golden.

Let the casserole cool slightly before serving. Enjoy this hearty meal with family and friends!