Blueberry Crumble Bars

Blueberry Crumble Bars are the ultimate easy dessert, made with layers of buttery crumble and a sweet, jam-like blueberry center. Baked thin and cut into generous squares, each piece delivers the perfect balance of crunchy topping and juicy filling. Using frozen blueberries keeps the process simple and fuss-free, while still giving you that rich, bakery-style flavor in every bite.

Love More Blueberry Desserts ? Try My Chewy Blueberry Cookies or this Blueberry Cheesecake Swirl Cookies next.

Why You’ll Love This Recipe

The combination of buttery crumble and juicy blueberry filling creates a dessert that feels special without requiring fancy ingredients or complicated steps. Easy to make, easy to share, and perfect for any occasion, these bars are a treat you’ll find yourself baking again and again.

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Ingredient List

For the Crust and Crumble:

• 3 cups all-purpose flour
• 1 cup granulated sugar
• 1 teaspoon baking powder
• ½ teaspoon salt
• Zest of 2 lemons (about 2 tablespoons)
• 1 cup cold unsalted butter (2 sticks)
• 1 large egg

For the Blueberry Filling:

• 5 cups fresh or frozen blueberries
• ½ cup granulated sugar
• 4 teaspoons cornstarch
• Juice of 2 lemons (about ¼ cup)

Substitution Notes: No fresh lemons? Bottled works in a pinch, though fresh really shines here. You can absolutely use frozen blueberries without thawing – just add five extra minutes to baking time. Out of butter? I’ve used coconut oil when solid, but the texture changes slightly. For the adventurous, try half whole wheat flour for a nuttier flavor, though kids might notice the difference.

Why These Ingredients Work

That lemon zest in the crumble? Game changer. I learned this trick from my grandmother who always said citrus makes berries “sing louder.” She wasn’t wrong – it brightens everything without overpowering those gorgeous berries. The cornstarch prevents soggy bottoms – learned that one the hard way after a few disasters where I served what looked like blueberry soup with crumbs floating on top. Not my finest moment.

Cold butter creates those perfect crumbly bits that make everyone think you’re some kind of baking wizard. When it hits the oven heat, those cold pieces create steam pockets that result in the flakiest, most tender texture. Room temperature butter just doesn’t give you the same magic. The egg acts like glue, holding everything together while adding richness, and that touch of baking powder gives the crust a shortbread-like tenderness that’s absolutely divine.

Essential Tools and Equipment

• 9×13-inch baking pan (metal works best for even browning)
• Large mixing bowls (2) – one for dry, one for berries
• Pastry cutter or fork (I prefer the fork method honestly)
• Whisk for combining dry ingredients
• Measuring cups and spoons (level those sugars!)
• Zester or fine grater (don’t skip the zest!)
• Parchment paper (optional but makes life easier)

How To Make Blueberry Crumble Bars

Prep Your Pan and Oven

Crank your oven to 375°F and grease that 9×13 pan like your life depends on it. Parchment paper is your friend here – makes cleanup a breeze.

Mix the Dry Ingredients

Dump flour, sugar, baking powder, salt, and lemon zest in a big bowl. Whisk it up good. That lemon zest smell? Pure heaven.

Create the Crumble

Toss in cold butter chunks and the egg. Grab a fork or pastry cutter and mash everything until it looks like chunky breadcrumbs. Don’t overthink it – messy is perfect here.

Form the Crust

Take half this mixture and press it hard into your pan bottom. Really pack it down – this is your foundation.

Prepare the Berry Filling

Mix the sugar, cornstarch, and lemon juice in another bowl. Fold in those gorgeous blueberries gently – nobody wants blueberry massacre.

Assemble the Bars

Spread berry mixture over your crust, then sprinkle remaining crumbs on top. Doesn’t need to look perfect – rustic is beautiful.

Bake to Golden Perfection

Bake 45 minutes until golden and bubbly around edges. Your kitchen will smell incredible.

Cool Completely

Walk away. Seriously. Let these cool completely or you’ll have delicious mush instead of neat bars. Patience, grasshopper.

You Must Know

Do NOT cut these warm. I repeat – do not cut them warm. I’ve ruined more batches being impatient than I care to admit. The filling needs time to set up or you’ll have a gooey mess on your hands. I know it’s torture when your kitchen smells like blueberry heaven, but walk away for at least an hour. Two hours is even better.

Here’s what happens when you wait – the cornstarch continues to work its magic as the bars cool, thickening that berry mixture into perfect jammy consistency. The crust firms up too, giving you clean slices instead of crumbly disasters. Trust me, I’ve served both versions to guests, and only one gets recipe requests.

Personal Secret: I keep extra crumble mixture in my freezer at all times. When I need a quick dessert, boom – half the work is done. I portion it into freezer bags, label with the date, and it keeps for months. Just thaw for twenty minutes before using. Smart, right?

Pro Tips & Cooking Hacks

Forgot to take your egg out early? Warm water bath for five minutes fixes that problem instantly. I do this more often than I’d like to admit because I’m terrible at planning ahead. Don’t overmix your crumble – those butter chunks create magic when they hit the oven heat. Think of it like making biscuits – overworking kills the flakiness.

Frozen berries work great but don’t thaw them first – they’ll make everything soggy and you’ll end up with purple pancakes instead of bars. I buy berries in bulk when they’re cheap and freeze them in recipe-sized portions. When the edges bubble and the top looks golden, you’re golden too. If the crumble still looks pale after forty-five minutes, give it another five or ten.

Here’s a trick from my disaster-prone early days – line your pan with parchment that hangs over the edges like little handles. Makes lifting the whole thing out so much easier for cutting. No more digging bars out with a spatula and ending up with a mangled mess.

Temperature matters more than you think. If your kitchen is really warm, pop that butter back in the fridge for ten minutes before mixing. Hot kitchens and baking don’t always play nice together. I learned this during one sweltering August when my “crumble” turned into paste because everything was too warm.

Flavor Variations & Suggestions

Mix up your berries – two cups raspberries instead of some blueberries creates this gorgeous mixed berry masterpiece that looks like summer in a pan. The tartness of raspberries plays beautifully with sweet blueberries. Try orange zest instead of lemon for a completely different vibe – it’s like sunshine in your mouth.

For chocolate fans, fold in half a cup of white chocolate chips with the berries. Sounds weird, tastes amazing. The chips get all melty and create these pockets of creamy sweetness that pair surprisingly well with the tart berries. My teenagers go absolutely crazy for this version.

Seasonal twist – add a tablespoon of fresh thyme leaves to the berry mixture. I know, I know, herbs in dessert sounds fancy and intimidating, but trust me on this one. Thyme and lemon are best friends, and it adds this subtle earthy note that makes people go “what IS that amazing flavor?” Every single time.

Make-Ahead Options

These actually get better overnight – the flavors marry together beautifully. Make them two days ahead if you want, just cover and leave on the counter. For longer storage, wrap individual bars and freeze them. They thaw perfectly in thirty minutes, and frozen bars are actually kind of amazing on hot summer days – like eating blueberry popsicles with crumble.

Want to get really ahead of the game? Make the crumble mixture a week early and store it in the fridge. I do this during berry season and keep containers of it ready to go. Sunday afternoon batch cooking at its finest. You can even portion the berries into freezer bags with the sugar and cornstarch already mixed in. Total game changer for busy weeknights when you want homemade dessert without the hassle.

The bars freeze beautifully whole too. I sometimes make double batches, cut one pan into bars, and freeze the other whole. When unexpected company shows up, I just thaw and serve. Nobody ever guesses it was frozen because the texture stays perfect. Just make sure to wrap everything really well – freezer burn ruins the party every time.

Recipe Notes & Baker’s Tips

This recipe works with any size blueberries – from tiny wild ones to those giant grocery store beauties. Super sweet berries? Cut the filling sugar down to one-third cup. High altitude bakers, reduce sugar by two tablespoons and add two more tablespoons flour. Works like a charm every time.

Serving Suggestions

Vanilla ice cream makes these bars downright sinful, but they’re perfect plain too. I serve them for brunch with strong coffee, pack them for picnics, and they disappear at every potluck. Want to look fancy? Dust with powdered sugar right before serving – instant bakery vibes.

How to Store Your Blueberry Crumble Bars

Store covered at room temperature for up to 3 days, or in the refrigerator for up to a week. For longer storage, wrap individual bars and freeze for up to 3 months.

Reheating: These are delicious at room temperature, but if you want them warm, just pop them in a 300°F oven for 5-10 minutes.

Allergy Information

Contains: Wheat (gluten), dairy, eggs

Gluten-free option: Substitute the all-purpose flour with a 1:1 gluten-free baking flour blend.

Dairy-free: Use vegan butter substitute in place of regular butter.

Questions I Get Asked A Lot

Can I use frozen blueberries?

Absolutely! Don’t thaw them first – use them straight from frozen and add an extra 5 minutes to the baking time.

Why are my bars soggy on the bottom?

Make sure you’re pressing that bottom crust firmly and using the cornstarch in the filling. Also, always let them cool completely before cutting.

Can I make these in a different sized pan?

For an 8×8 pan, cut all ingredients in half. For a larger pan, you might need to adjust baking time slightly.

How do I know when they’re done?

The top should be golden brown and you should see the blueberry juices bubbling around the edges.

Can I double this recipe?

Yes! Use two 9×13 pans or one large sheet pan, and you might need to add 5-10 minutes to the baking time.

💬 Tried this recipe? Leave a comment and rating below! I love hearing about your baking adventures and any creative variations you try!