Melt butter in skillet, sauté onion and garlic until tender. Cut zucchini into 1/2-inch slices. Peel eggplant and cut into 1/2-inch slices. Dredge zucchini and eggplant in flour. Add to onion skillet mixture with green peppers and simmer covered for 30 minutes. Add tomatoes, salt, oregano and pepper and cook 15 minutes longer.Serves 6.