Blueberry crumble bars are a delicious, portable way to lock the fresh flavor of summer between sweet, crunchy crumble layers. They are a crowd-pleaser any time of the year!
This recipe is specifically made to feed a LARGE crew. It makes an entire half-sheet tray of bars! This makes them perfect for taking to a crowd, like the 4th of July. We actually made them to share at Christmas!
Not trying to feed an army? No problem! I have tips on making a 9×13 sized portion in the recipe notes.
These blueberry crumble bars are easy to make with ingredients you likely already have in your pantry, fridge, and freezer. They come together quickly and inexpensively!
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Berries, berries everywhere
We live in berry central up here in Western Washington. Blackberries grow wild on invasive brambles. Raspberry and strawberry farms are historic fixtures in our region. Blueberries are often grown at local u-pick sites where you can buy as many as you can stand to pick! We love to grow or buy produce in bulk, especially berries.
We always harvest some sort of berries in bulk each year and simply freeze them. This means we always have local berries on hand so we get the best, freshest produce for less. We also support local farms, reduce our food miles, and avoid excess plastic waste as we wash and reuse gallon freezer bags.
Last summer, I went to a blueberry u-pick farm with my sister and niece and loaded up on about 13 lbs of fresh berries. It was such a nice day out and my husband and I have been snacking on them ever since!
Read: How to Freeze Berries
How to Use Up Frozen Berries
When your freezer is full of gallons and gallons of frozen berries…you should definitely make a plan to use them beyond an occasional sprinkle in some oatmeal.
I was looking for a recipe to share with our families during Christmas and wanted to incorporate some berries. Fortunately, I had plenty to work with!
Advice for Using Frozen Berries
The main thing to know about working with frozen berries is that you typically need to thaw them. If you don’t, they will release way too much moisture when cooking and make a soppy mess. We found that out the hard way when we made a giant tray of marionberry crisp for our wedding. Fortunately, the apple crisp came out perfectly!
Since we essentially make a pie filling to add to these crumble bars, our berries are a little more forgiving. I still recommend setting them out to thaw for a bit before cooking, but we added frozen berries to the pie filling about halfway through and had no problems.
You can simply place them on a large, shallow dish to thaw on the counter for about an hour or two. We used our berries partially thawed. You could also put your bag of frozen berries in the fridge overnight (be sure to put them in a container in case of leaks!).
How to make a giant batch of any recipe
We were inspired by this recipe for raspberry crumble bars from Half Baked Harvest. We loved the idea of berry-packed bars we could pick up with our fingers!
To make an extra-large portion of the bars, we slightly modified the instructions for her crumble and applied King Arthur’s advice to multiply ingredients by 1.5 to make a half sheet tray portion. We also added some whole wheat flour for extra texture and flavor and made our own blueberry pie filling.
On our first recipe, we used about over 2 quarts of blueberries and had some messy overflow in the oven. We since reduced the amount of berries to 1.5 quarts (6 cups) and have had success ever since.
Customize these big batch berry crumble bars with your favorite berry
You don’t need to be a purist and stick to this recipe perfectly. We can’t wait to try this recipe with marionberries, raspberries, or strawberries! We were so tempted to mix in marionberries with our blueberries, but didn’t want to alter the flavor.
Tip #1: Keep the proportions of berries the same
This will help make sure you don’t have too much or too little filling.
Tip #2: Start with less sugar
Depending on the berry you use, you may need more or less sugar than this recipe requires. A tart berry like a cranberry will need more sugar while a sweet strawberry may need less.
Blueberry Crumble Bar Recipe Instructions
Adapted from Buttery Raspberry Crumble from the Half Baked Harvest
Preheat your oven to 350.
Butter a half sheet baking tray.
In your food processor, combine oats, flours, brown sugar (make your own if you’ve run out!), 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.
If you want to eat these as bars with you can pick up and eat with your fingers, 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.
If you want to eat these as a crumble and don’t mind needing a fork and plate for them, add 1/3 of your crumb layer to your half sheet tray and press down. Be sure to make an even layer. Bake in the oven for 10-12 minutes.
While the base layer is baking, 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 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 bars to cool completely. If they are still warm, they will not be firm enough to pick up. Cut into squares or bars as desired.
Big Batch Blueberry Crumble Bars
- Half sheet tray
- 3 cups oats
- 1 cup whole wheat flour
- 1 1/2 cup all-purpose flour
- 1 1/2 cup brown sugar
- 1 1/2 tsp baking powder
- 3 sticks cold butter
- 2 quarts frozen blueberries partially thawed
- 1 1/2 cups sugar
- 1/3 cup corn starch
- 3 tbs lemon juice
- Preheat your oven to 350.
- Butter a half sheet baking tray.
- 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.
- 2 cups oats
- 3/4 c whole wheat flour
- 3/4 c all-purpose flour
- 1 cup brown sugar
- 1 tsp baking powder
- 2 sticks butter
- 1-2 tbs water
- 4 cups blueberries
- 3/4 cup sugar
- 1/4 cup corn starch
- 2 tbs lemon juice
Have you tried this recipe? Did you make it for an event? How did it go? Tell us in the comments!