Cook the sausage patties to an internal temperature of 165 degrees F on the grill or in a pan.
Place sliced peppers and onions on a baking sheet. Lightly coat with oil and dust with garlic powder. Bake at 375 degrees F for 10 minutes or until softened.
Lay out the slices of bread and spread butter on one side. Season buttered side with garlic powder and parmesan.
On the unbuttered side, layer a slice of mozzarella, sausage patty, peppers and onions and finish with more mozzarella.
Close sandwich and place in a nonstick pan on medium heat. Cook for approximately one minute, pressing down with a spatula. Flip and repeat until the cheese is melted and bread is golden brown. Remove, cut and serve.