Thaw rhubarb and peaches, if frozen. Do not drain. For filling, in a large mixing bowl stir together sugar, flour, and salt. Add rhubarb and peaches and their juices, then gently toss till coated. Add 2 cups of the bread cubes. Drizzle with 2 tablespoons of the melted margarine or butter, then toss till mixed. Transfer fruit filling to an ungreased 8x8x2-inch baking dish.

For topping, in a medium mixing bowl combine the remaining bread cubes and orange peel. Drizzle with the remaining melted margarine or butter, then toss till mixed. Sprinkle the bread topping on top of the fruit filling. Bake in a 375 degree F. oven for 25 to 35 minutes or till fruit is tender and topping is golden. Serve warm. If desired, dollop with whipped cream.