Layer the hashbrowns, red bell pepper, onion, and spinach and half the cheese (if using) in a 9 x 13 inch casserole dish.
Whisk the eggs, milk, garlic powder, salt, and pepper in a bowl. Pour evenly over vegetable mixture. Top with the rest of the cheese (if using).
Bake 50 - 60 minutes, until the center is cooked through and the cheese is golden (if using). Serve warm.
Frozen hashbrowns. I used plain frozen hashbrowns and didn't unthaw them. You can also use seasoned hashbrowns - just adjust the seasonings to taste.Spinach. I like using spinach or any quick-cooking green in this recipe. I recommend steaming fresh spinach either on top of the stove or in the microwave.You can also use frozen spinach. Be sure to thaw and drain it completely before adding to the casserole.Bell peppers. Feel free to swap in any bell pepper. I like the red bell pepper for the color and hint of sweetness but other colors work great.Seasonings: If you are not using cheese, increase the salt by up to ½ teaspoon. You can add paprika, onion powder, or other dried herbs such as oregano to the egg mixture.