Preheat oven to 350°F. Slice off tops from peppers; scrape out centers to remove seeds and membranes. Combine all remaining ingredients except green onion in medium bowl; mix well. Evenly stuff peppers with sausage mixture. Place in lightly greased deep 3-quart casserole dish. Bake, covered, 20 minutes. Uncover; bake 5 to 10 minutes more or until peppers are fork-tender and filling is set. Garnish with green onion, if desired. Serve hot. Refrigerate leftovers.
For a pretty presentation, slice 6 small peppers lengthwise in half through stem; scrape out centers to remove seeds and membranes. Proceed as directed, serving 2 halves to each guest.
Serve with mixed salad of carrot, radish and cucumber slices drizzled with a vinaigrette.