Place sausage on a 15-inch x 10-inch x 1-inch baking pan.
Bake at 375˚F for 15 to 20 minutes or until sausage is no longer pink and an internal temperature of 165˚F is reached, 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 350˚F for 65 to 70 minutes or until set and golden brown and an internal temperature of 165˚F is reached.
Let stand 10 minutes before serving.
Serve with salsa or picante sauce if desired.