Preheat your oven to 400°F (200°C).

Combine peaches, sugar, and tapioca flour in a mixing bowl. Let sit for 15 minutes.

Mix flour, brown sugar, and salt in a food processor. Add butter pieces and pulse to achieve a clumpy texture. Stir in pecans and oatmeal.

Roll out your pie crust to fit a 9-inch pie dish and transfer it carefully into the dish.

Pour the peach mixture into the pie crust and top with crumble.

Bake at 400°F (200°C) for 30 minutes, then reduce temperature to 350°F (175°C) and bake for an additional 30 minutes.

Cool for at least 30 minutes before serving.