Sauté onion, celery leaves, and parsley in butter in a large skillet until tender. Add next 8 ingredients; stir lightly.
Stuff mixture into green peppers. Place in a lightly greased shallow baking dish, and bake at 350° for 20 minutes. Top peppers with cheese. Bake an additional 5 minutes or until cheese melts.
Oxmoor House Homestyle Recipes