Place yogurt in a small bowl and stir until creamy smooth. Add lemon and stir together. (Note: If you do not stir the yogurt first, the lemon juice will make the yogurt curdle.) In a separate shallow dish or bowl combine the bread crumbs, garlic powder and salt to taste; mix together.
In a 9x13 inch baking dish place 1 scant pat of butter or margarine for each chicken breast. Rinse chicken breasts and pat dry. Dip each breast in the lemon/yogurt mixture, then in the bread crumb mixture (coating completely but not heavily).
Place coated chicken in the baking dish and top each breast with a full pat of butter or margarine. Sprinkle with chopped parsley and bake in the preheated oven for 1 hour. Let cool for 5 to 10 minutes before serving.