Mix together flour, sugars, nutmeg, and salt in a bowl. In a large bowl, beat the egg and orange juice together. Add the rhubarb, peaches, and zest. Sprinkle dry ingredients over the top and toss gently to combine.
Pour the filling into the piecrust. Sprinkle with topping and bake on the bottom 1/3 of the oven for about 1 hour, until the filling bubbles.
Put all ingredients into a food processor and pulse until mixture resembles a coarse meal.
Professional Recipe: This recipe was provided by a chef, restaurant or culinary professional and makes a large quantity. The Food Network Kitchens chefs have not tested this recipe in the proportions indicated and therefore cannot make any representation as to the results.