Heat oven to 350. In large saucepan cook onion in oleo until tender. Stir in flour, salt, sage and pepper. Cook until bubbly. Stir in broth, milk and mushrooms. Cook and stir until mixture boils and is slightly thickened. Stir in remaning ingredients except swiss cheese. Spoon in to ungreased 12 x 8 inch ( 2 quart) baking dish. Sprinkle with swiss cheese. Bake uncovered at 350 for 20 to 30 minutes until hot and bubbly. If desired sprinkle with chopped parsley.