In a saucepan, combine first five ingredients (cornstarch through lemon juice) until smooth. Bring to a boil; cook and stir for 1 to 2 minutes or until thickened. Cool, cover and refrigerate.
Preheat oven broiler.
Flatten turkey to 3/4-inch thickness. Combine oil and pepper; rub over both sides of turkey breasts. Broil 4 to 6 inches from heat for 5 to 7 minutes on each side until turkey is cooked through.
Just before serving, stir grapes into sauce. Serve turkey with cranberry-grape sauce.
Notes
*LEANNE’S HINT: if you don’t want to use turkey, use chicken instead!