Preheat oven to 425° F. Place the chicken in a shallow roasting pan or a 9-by-13-inch cake pan. Sprinkle with the oregano, then pour on the sauce. Sprinkle with the Parmesan and bake for 12 to 15 minutes or until the sauce is hot and the cheese is melted. Season with pepper to taste. Serve with mixed greens dressed with a vinaigrette.