Using hands, shred 1 cup of leftover bread into 1/2-inch long pieces.
Bake bread cubes on a baking sheet with a lip in a preheated 200° F oven for 15 minutes; remove from oven and set aside. Increase oven temperature to 325° F.
While cubes bake, make streusel: cook almonds in skillet over medium heat, stirring often, until lightly browned. Add margarine; melt. Stir in torn bread and 1/3 cup brown sugar; cook until well mixed and caramelized. Set aside.
Toss cubed bread with drained peaches, 1/2 cup reserved juice, 1/4 cup brown sugar and nutmeg.
Pour filling into greased 8x8x2-inch pan; dot with 1/2-inch chunks of margarine.
Sprinkle top with streusel.
Bake for 25-30 minutes until bubbling.
Serve with vanilla ice cream or whipped cream, if desired.