Feed a crowd with these blueberry crumble bars! They are sweet, crunchy and full of fresh berry flavor. They're easy to make with frozen berries and you can use any type of berry you like!
In your food processor, combine oats, flours, brown sugar, and baking powder until the oats are ground. Cube cold butter and add it to the food processor while pulsing until a dough forms. Your dough should stick together when pressed. If not, add up to 2 tbs ice cold water.
Add 1/2 of your crumb layer to your half sheet tray and press down. Be sure to make an even layer. Bake in oven for 12-15 minutes. (See note below on crumb layer proportions)
While the base lyer is cooking, add thawed blueberries, corn starch, and sugar to a large pot. Stir to coat the berries in corn starch to avoid clumps. Cook down until the cornstarch thickens up. Add 2 tbs of lemon juice.
Spread the blueberry mixture over the the base layer. Add the remaining 1/2 of the crumble mixture on top of the blueberry mixture. Bake for 40 minutes until crumble turns golden brown.
Allow to cool completely so the blueberry mixture firms up. Cut into squares or bars as desired. Store in the fridge to keep fresh.
Notes
The berries can be changed out to your preference! Consider substituting blackberries, raspberries, or strawberries instead. If cooking with frozen berries, allow to thaw first.You can use whole wheat and all-purpose flour like I did or you can sub all whole wheat or all all-purpose. If you do all whole wheat, you may need to add slightly more water in the food processor.Note on crumb layer proportions: The recipe I adapted calls for 1/3 of the crumb as the base layer and the remaining 2/3 as the top layer. This made delicious bars, but they were not finger-food you could pick up and eat without making a mess. If you want bars that are finger-friendly, use 1/2 of the crumb as the base and 1/2 as the top layer.This recipe makes a BIG batch to feed a crowd. If you would like a single 9x13 instead, you need to follow the same instructions with these smaller quantities.