Preheat oven to 350°F.
In large skillet over medium heat, brown sausage 8-10 minutes (safe internal temp. 160°F). Transfer to large bowl with prepared stuffing, reserving drippings in skillet.
Meanwhile, use knife to cut tops off apples. Use spoon to scoop out flesh, discarding seeds and core, leaving ⅛-inch-thick shells. Chop scooped apple and tops (stems removed).
Add butter, onion, parsley and chopped apple to skillet with reserved drippings. Cook 3-5 minutes or until onion and apple are softened. Remove from heat. Stir in sausage and stuffing.
Spoon mixture into apple shells, then arrange in 13x9-inch glass baking dish. Pour vinegar around apples. Bake 40 minutes.
Serve immediately, refrigerating any leftovers.
