Place sausage on a 15 x 10 x 1-inch baking pan. Bake at 375 degrees for 15 to 20 minutes or until sausage is no longer pink, turning once; drain and slice into 1/4-inch coins. In large bowl, combine eggs, milk, mustard, salt, and pepper. Add hash browns, sausage, cheese, sweet red pepper, and green onions; mix well. Pour into a greased 13 x 9 x 2-inch baking dish. Cover and refrigerate overnight. Remove from the refrigerator 30 minutes before baking. Bake, uncovered, at 350 degrees for 65 to 70 minutes or until set and golden brown. Let stand 10 minutes before serving. Serve with salsa or picante sauce if desired. Makes 12 to 15 servings.