Blueberry Crumble Bars

Why I Love Baking These Blueberry Bars

• Blender magic. I use the blender to make the streusel mixture for my bars. Blending is quick and convenient, but you can always mix it by hand, too.
• The crumble doubles as the crust. It makes preparing these bars even easier. Press half into the pan, and crumble the rest on top of the blueberry filling.
• Chilling the bars gives them the best texture. Refrigerating the bars before baking yields a crunchy topping and sturdy crust, and also prevents the crumble and crust from spreading.
• An easy make-ahead dessert. These bars store well in the fridge, so I’ll usually make them the day before a summer gathering.

Ingredients Needed

Here’s a look at the ingredients you’ll need to make the crumble and blueberry filling for this easy summer dessert bars recipe. Find the full ingredient list in the printable recipe card at the bottom of the post.

Blueberry Filling

• Blueberries – This is a great recipe to make during blueberry season when the berries are ripest. That being said, frozen blueberries are a great alternative if fresh aren’t available. See below.
• Lemon Juice – Brightens and enhances the blueberry flavor. You could substitute lemon juice with white vinegar in a pinch.
• Cornstarch – I toss the blueberries in a mixture of cornstarch and sugar before baking to thicken the filling. If you’re using flour, you’ll need about twice the amount.

Crumble Topping

• Flour – I recommend all-purpose flour, since I haven’t tested this recipe with alternatives yet.
• Oats – I use old-fashioned rolled oats. If you’re mixing the crumble by hand instead of in the blender, consider using quick oats instead. They’ll soften more easily.
• Brown Sugar – I use light brown sugar, but you can use granulated sugar or dark brown sugar if needed.
• Butter – Cold from the fridge, like you’d use to make a pie crust. I always bake with salted butter as a personal preference, but you can use unsalted. Cutting the butter into cubes makes it easier to cut into the dry ingredients.

Can I Use Frozen Blueberries?

Yes, I’ve successfully made these blueberry bars with fresh or frozen blueberries. If using frozen, thaw the berries completely and pat them dry before tossing them with the cornstarch. I actually love to freeze my own blueberries when they’re in season, so I can use them in baking recipes like my blueberry crisp and blueberry banana bread year-round!

How to Make Blueberry Crumble Bars

These crumbly, buttery blueberry bars come together easily, with just a short chilling time before they go into the oven. I can prepare my bars the day before and leave them in the fridge overnight, so they’re ready to bake before a potluck or barbecue. Here’s how to make them.

1. Make the crumble/crust mixture. Start by pulsing the flour, oats, brown sugar, and salt in the blender or food processor. Once that’s combined, add in the cold butter and pulse again. You want the mixture to look a bit like coarse sand.
2. Shape the crust. Next, divide the mixture in half. Press one half into a greased 9×9 pan to make the base. Set this aside.
3. Make the blueberry filling. Meanwhile, toss the blueberries with sugar and cornstarch, then add the lemon juice.
4. Assemble the bars. Spread the blueberries on top of the prepared crust. Then, sprinkle the reserved crumble from earlier on top of the filling. Gently press the topping into the blueberries. Afterward, place the bars into the fridge for 30 minutes.
5. Bake. Bake these blueberry crumb bars at 350ºF for 35-40 minutes, until the blueberries start to bubble.

Tips for the Best Blueberry Bars

• Blending vs. by hand. I use my blender to combine the ingredients, but you can use a food processor or mix the crumble by hand. If elbow grease and a pastry cutter are your preferred method, I recommend that you use quick oats instead of rolled oats.
• Don’t skip the cornstarch. Coating the fresh blueberries in sugar and cornstarch sweetens the filling at the same time that the cornstarch helps to thicken it.
• The blueberries will begin to bubble as they bake. This means the bars are just about done! Whatever you do, don’t over-bake the bars. This will make the crust and the topping overly hard and crunchy.

Recipe Variations

• Add lemon. If you love the blueberry lemon combo in desserts like my lemon blueberry blondies, consider amping up the lemon flavor in these blueberry bars. Zest the lemon before you juice it for the filling, and fold the fresh zest in with the blueberries.
• Crust options. If you wanted to make these blueberry bars with a graham cracker crust, that’s also a great option.
• Use pie filling instead. While I love the flavor of fresh blueberries, if you’re short on time, swap the homemade filling with your favorite canned blueberry pie filling as a shortcut.
• Change up the berries. Substitute strawberries, blackberries, or raspberries for the blueberries in the recipe, or make mixed berry crumble bars.
• Add a pinch of cinnamon. Add a teaspoon of cinnamon (or nutmeg) to the crumble mixture for a touch of warm spice.

Storage and Freezing Instructions

• Store the bars in the fridge. I recommend storing these bars in the refrigerator, airtight, for up to 3 days. You can also store them at room temperature, but I would only advise it for up to 24 hours. At room temperature, the moisture in the blueberries causes the topping to become soggy. Refrigeration helps slow this process.
• Freeze. These blueberry crumble bars freeze very well. Allow them to thaw in the refrigerator, and you can enjoy them chilled or at room temperature.

More Summer Berry Desserts

• Blueberry Buckle
• Strawberry Cobbler
• Blueberry Bundt Cake
• Blueberry Shortcake
• Berry Crisp
• Blackberry Cobbler