Combine the brown sugar, flour, oats, and baking powder in a bowl. Cut in the butter to make the crust and crumble topping.
Add half of the crust to a brownie pan. Pressing the crust to the bottom and making it flat.
Cook the blackberries, brown sugar, and corn starch to a pan. Cook over medium heat for 5 minutes.
Add the blackberry mixture to the pan then sprinkle with chocolate chips and raspberries.
Top the oat bars with the remaining crumb topping.
Bake at 350 degrees for 33 minutes.