Place sausage on a 15-inch x 10-inch x 1-inch baking pan. Bake at 375ºF for 15–20 minutes or until sausage is no longer pink, turning once; drain and slice into 1/4-inch coins. In a large bowl, combine the eggs, milk, mustard, salt and pepper. Add the hash browns, sausage, cheese, sweet red pepper and green onions; mix well. Pour into a greased 13-inch x 9-inch x 2-inch baking dish. Cover and refrigerate overnight.
Remove from the refrigerator 30 minutes before baking. Bake, uncovered, at 350ºF for 65–70 minutes or until set and golden brown. Let stand 10 minutes before serving. Serve with salsa or picante sauce if desired.