In a medium bowl, mix together all topping ingredients with a fork until large crumbs form. Refrigerate until firm (while making the rest of the pie). This can also be made up to 2 days ahead of time.
Make the pie crust according to recipe instructions. Roll out and transfer to a pie plate. Do not prick the bottom. Refrigerate while you make the filling.
In a small bowl, whisk together all dry ingredients. Place the peeled and sliced peaches in a large bowl and sprinkle the dry ingredients on top. Mix together until well combined.
Pour peach filling into prepared pie crust. Crumble crumbs over top of peaches, breaking up any super large chunks with your fingers.
Place pie on parchment or foil-lined baking sheet to catch drippings. Bake at 450° F for 10 minutes. Drop temperature down to 350° F and continue to bake for 50-60 minutes, shielding pie crust edges as necessary if getting too dark. To check for doneness, slide a butter knife through the filling. If there is little to no resistance, the peaches are fully cooked through.
Remove from the oven and allow to cool before serving. Serve with vanilla ice cream or freshly whipped cream. If peaches are extra juicy and filling is oozing, refrigerate the pie to
To make ahead, the whole pie can be frozen unbaked. Assemble and wrap the entire pie in plastic wrap, followed by foil. Alternatively to foil, place the plastic wrapped pie in a large (2 gallon) ziptop bag and remove as much air as possible from bag. Unwrap pie and bake straight from the freezer at 350 degrees F for 1 1/2 hours (90 minutes). Will keep in the freezer for 3 months.