For biscuit topping, in a medium mixing bowl stir together the flour, the 1/4 cup sugar, baking powder, and cinnamon. Cut in margarine or butter until mixture resembles coarse crumbs. Combine egg and milk; set aside.
For filling, in a medium saucepan combine the 1/2 cup sugar and cornstarch; add water. Stir in peach slices, lemon peel, and lemon juice. Cook and stir until thickened and bubbly. Gently fold in raspberries. Return just to boiling, stirring gently to avoid breaking up the fruit. Transfer hot filling to a shallow 2-quart casserole.
Add the egg mixture all at once to the dry ingredients, stirring just until moistened. Immediately spoon topping into 6 to 8 mounds on hot filling. Sprinkle with the 1 teaspoon sugar.
Bake in a 400 degree F. oven for 20 to 25 minutes or until a toothpick inserted into topping comes out clean. Serve warm with ice cream or sweetened whipped cream. Makes 6 servings.