Preheat the Oven to 350 degrees F and lightly oil a 9-inch square or round baking dish (I used a 9-½-inch cast iron oval baking dish).
Combine all of the ingredients for the crumble topping in a mixing bowl and stir well to combine. Refrigerate for 5 minutes while you prepare the rest of the recipe.
Add the sliced peaches to a large mixing bowl, along with the rest of the ingredients for the peach filling. Gently toss everything together until combined.
Transfer the peach filling to the oiled baking dish, then evenly spread the crumble topping on top. Bake on the center rack of the oven for 40 to 50 minutes, or until topping is golden-brown and crispy.
Allow crumble to cool 15 minutes before serving with ice cream.