In a saucepan over medium heat, saute onion in margarine until tender.
Stir in chicken broth, zucchini, corn, green chile peppers, salt and pepper. Heat to boiling; reduce the heat, cover and simmer until the zucchini is tender, about 5 minutes.
Stir in milk and heat thoroughly. Add Monterey Jack cheese and stir until melted. Serve hot