1. Pre-heat the oven to 350 degrees.
2. Roll the pie crust out and transfer to a 9-inch pie pan (if you have a deep dish pan, that’s preferred). To help weigh the crust down, you can add parchment paper and add dry beans or pie weights (as shown in the photos/video). Or, you can prick the crust a few times with a fork before baking.
3. Pre-bake the pie crust at 350 degrees for 10-15 minutes. (This will make the bottom of the crust more sturdy for the berry pie filling.) When the pie crust is done pre-baking, let it cool for a few minutes before adding the filling and topping.

For The Triple Berry Pie Filling:

1. While the pie crust is pre-baking, mix up your filling. In a large bowl, combine berries, sugar, cornstarch, lemon juice, and a tiny pinch of salt. Gently stir with a flexible spatula to coat the berries.

For The Crumble Topping:

1. Next, make the crumble topping. In a medium bowl, combine softened butter, brown sugar, oats, flour, vanilla, and salt. Combine with two forks, a pastry blender (or your fingers!) until the flour and brown sugar are hydrated with the butter and small clusters and clumps form.

Assemble & Bake The Pie:

1. Now, assemble the pie. Add berry filling to the pre-baked crust and top with crumble topping.
2. Place the pie pan on a baking sheet (in case of bubbly spills!) and bake the pie at 350 degrees for 55-65 minutes, or until the top is golden** and the filling is visibly bubbling. (If it’s not bubbling, the cornstarch can’t thicken the filling.)