Combine all ingredients except the olive oil and the three optional items in a large bowl and mix well.
If making sausages, use the sausage attachment on a heavy-duty mixer, stuff the casings with the mixture and twist and tie to make eight 4-inch links. Or shape into eight 3-inch-long lozenges, slightly fatter in the middle, formed around metal skewers or into 8 patties.
Preheat grill or broiler. If the sausages are in casings, prick with a fork 2 to 3 times and brush with oil.
Grill or broil 3 to 4 minutes on each side until cooked through. For lozenges, brush with oil and cook 3 to 4 minutes on each side.
For patties, brush with oil and grill 4 to 5 minutes on each side or sauté over high heat.
If desired, sausages may be threaded on skewers alternately with green pepper pieces and onion quarters before grilling.
Servings: 4