Blueberry Crumble Bars (Big Batch!)

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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!

blueberry crumble bars big batch

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!

Read: Why You Need to Keep a Well-Stocked Pantry

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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.

Our berry harvest washed and drying before heading to the freezer!

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.

blueberry crumble bars

Big Batch Blueberry Crumble Bars

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!
5 from 7 votes
Prep Time 30 mins
Cook Time 40 mins
Total Time 1 hr 10 mins
Course Breakfast, brunch, Dessert
Cuisine American
Servings 24

Equipment

  • Food processor
  • Half sheet tray

Ingredients
  

Crumble

  • 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

Pie Filling

  • 2 quarts frozen blueberries partially thawed
  • 1 1/2 cups sugar
  • 1/3 cup corn starch
  • 3 tbs lemon juice

Instructions
 

  • 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.

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 9×13 instead, you need to follow the same instructions with these smaller quantities.
  • 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
Keyword berries, berry crumble, big batch, blueberry, blueberry crumble, crumble, summer desserts
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16 Comments

  1. These look so good!
    I miss our blueberry plants!
    We used to have a whole bunch!

    I will keep in mind to cook up a sauce like you did with yours.

    Pinning this recipe!

    Thanks for sharing it at the Sunday Sunshine Blog Hop!

    Blessings,
    Laurie
    Ridge Haven Homestead
    Homestead Blog Hop
    Sunday Sunshine Blog Hop

    1. Laurie, thanks for visiting! These really are delicious and I can imagine the bags of berries in your freezer from when you had your berry plants! That sounds wonderful.

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