This Triple Berry Pie isn't only easy but is fresh and delicious! This fruity dessert has an amazing berry pie crumble on top and is perfect all year long.
Preheat oven to 400 degrees.
In a large mixing bowl combine the blackberries, blueberries, raspberries, sugar, flour, cornstarch, lemon juice, lemon zest, and vanilla. Toss to combine until evenly coated. Place in refrigerator until needed.
In a medium mixing bowl combine the oats, brown sugar, flour, cinnamon and salt. Mix, then using a pastry blender, cut in the butter until pea-size clumps form. Place in refrigerator until needed.
Roll out or place a pre-made pie crust into a 9-inch pie dish. Press gently into the bottom of the pan, then flute the edge or crimp using a fork.
Add cold filling, then sprinkle on the topping. It will be a generous amount.
Place in the oven and bake for 30 minutes, then cover with foil and continue baking for 20-25 minutes. Tent the foil at the 45 minute mark to prevent the crust and topping from getting too brown.
Remove from the oven and allow the pie to cool at room temperature for 2 1/2 hours before serving, or allow the pie to cool at room temperature for 1 hour, then 1 hour in the refrigerator before serving.