I reach for this Breakfast Casserole whenever I want a warm, hearty morning meal that feeds a crowd without much fuss. It's loaded with browned sausage, tender bell peppers, and melted Gruyere and cheddar cheese throughout the eggs, all baked into a golden, bubbly dish everyone loves. I make it for Christmas morning, Easter brunch, Mother's Day, potlucks, and busy weekends because it travels well and you can make it ahead. Leftovers stay fresh in the fridge for 3 to 4 days or freeze for up to 3 months.