Fit pie crust into a deep-dish glass pie plate and flute edges.
Place pie weights or dry beans on top of a circular piece of parchment paper fitted inside the crust. TIP: I usually cut a piece of parchment as big around as a ten-inch skillet lid, which I trace around the paper with a knife, and then easily trim what didn’t cut.
Blind bake the pie crust for 20 minutes, then remove weights and parchment and allow the crust to cool down while you prepare the filling. Lower oven temperature to 350°F.
Mix together the granulated sugar with corn starch and toss with berries.
Place filling into the crust.
Stir together the flour, brown sugar and oats for the topping and mix with half the melted butter.
Sprinkle over the top of the filling, then drizzle with the remaining butter.
Bake the pie for 60-75 minutes or until the top is golden brown.