Pare very thinly the bright-colored rind from the oranges (no white). Blot the peel on paper towels to remove any excess oil. Put peel in a 4 cup screw-top jar. Add 2 cups vodka. Close jar. Store in a cool, dark place for 2 days or until the vodka has absorbed the flavor. Remove peel and add remaining vodka. Close jar and add remaining cup of vodka. Close the jar and store in a cool dark place at least 1 month to age.