Preheat the oven to 350 degrees F (175 degrees C).
Place the peaches into the bottom of a buttered 9 inch square baking dish. Cut each slice of bread into 4 strips, and place over the peaches. In a medium bowl, whisk together the sugar, flour, egg and margarine; pour over the bread.
Bake for 35 to 45 minutes in the preheated oven, or until golden brown.