Begin by thinly slicing one of the oranges, cut the slices in half, and set aside to be used as garnishes. Slice the remaining orange in half, cut one half into thin slices, and set aside for later use. Carefully remove the outer peel from the remaining half of the orange and place it in a large bowl. Add the sugar and mash it into the orange peel to help release the flavorful oils from the peel. Add the wine, orange juice, white grape juice, and Cointreau, and stir well to combine. Cover and chill in the refrigerator for 30 minutes or more to allow the flavors to blend. Remove the orange peel and discard it. Transfer the mixture to a large pitcher and add the reserved whole slices of orange. Serve in tall ice-filled glasses and garnish each with a half slice of orange.

Yield: 1 1/2 Quarts