How to bake mixed berry crumble bars

A good way to use fresh Berries, bake the delicious Mixed Berry Crumble Bars, a wonderful Summer Dessert.

Mixed Berry Crumble Bars
Ingredients:
Dough/Topping
3 cups Flour
1 cup Sugar
1/2 tsp Salt
1 tsp Baking Powder
1 tsp Nutmeg
1 Egg
1 tsp Vanilla
1 cup Butter, cold/cubed
1/4 cup Oats

Filling:
4-1/2 cups mixed Berries
(we used Strawberries/Blackberries)
Zest of a Lemon
1/2 tsp Nutmeg
1/2 cup Sugar
5 tsp Cornstarch

Combine Flour, Sugar, Salt, Baking Powder & Nutmeg.
Whisk together Egg & Vanilla and add to Flour Mixture.
Work in Butter until crumbly.
Remove 1/3 of Dough for Topping, add Oats & set aside.
Preheat Oven 350° F
Line 9×13 pan with Parchment Paper, coat with Cooking Spray.
Press in remaining Dough to form a Crust.
Combine all Filling Ingredients and spread out Berry Mixture evenly over Crust.
Sprinkle Crumble Topping over Berries.
Bake 50 - 55 Minutes.
Cool completely on Wire Rack.
Refrigerate overnight, to make the cutting easier.
Cut in 15 equal sized Mixed Berry Crumble Bars.
Enjoy!