Blueberry Crumb Bars Recipe (Buttery, Jammy & So Simple)
This Blueberry Crumb Bars Recipe gives you a buttery shortbread base, juicy blueberry filling, and a golden crumb topping—all in one easy pan and with no mixer needed.
I’ve been making some version of these blueberry crumb bars for years, and they’re still the first thing my kids ask for when blueberry season hits. Think of them as a blueberry bar dessert that sits somewhere between a cookie, a pie, and a fruit crumble. They’re sturdy enough to hold in your hand, yet soft and jammy in the center, with a crisp, buttery crumb crust and topping that stays delicious for days.
You can bake these with fresh summer blueberries or frozen ones from your freezer stash. They’re fantastic for picnics, potlucks, school events, and “I just need something sweet with my coffee” moments. And because everything is pressed into one pan, there’s no fuss—no rolling, no fancy tools, and no pastry degree required.
Why You’ll Love This Recipe
- Simple pantry ingredients – Flour, oats, sugar, butter, and blueberries; nothing unusual or hard to find.
- No mixer needed – You can stir the whole blueberry crumb bar recipe together with a bowl and a spoon.
- Perfect make-ahead dessert – These blueberry crumb squares slice cleaner and taste even better the next day.
- Fresh or frozen berries – Use fresh blueberries at their summer peak or frozen berries when they’re cheaper.
- Great for feeding a crowd – One 9×13 pan of homemade blueberry bars makes enough for parties, picnics, or bake sales.
- Freezer-friendly – These blueberry cookie bars freeze well, so you can stash some for later.
- Flexible and forgiving – Gluten-free, less sugar, or mixed berries? Easy tweaks, still delicious.
- Multi-purpose treat – Serve warm with ice cream for dessert or at room temp as a coffee-break treat.
Ingredients
Let me walk you through what you’ll need for these easy blueberry crumb bars. Nothing fancy, just good basics that love each other.
For the buttery crumb crust and topping (blueberry shortbread base + crumble):
- 3 cups (375 g) all-purpose flour
- 1 cup (100 g) old-fashioned rolled oats (for a rustic blueberry oat crumble texture)
- 1 cup (200 g) granulated sugar
- ½ cup (100 g) light brown sugar, packed
- 1 teaspoon baking powder
- ½ teaspoon fine sea salt
- 1 teaspoon ground cinnamon (optional, but so cozy with blueberries)
- 1 cup (2 sticks / 226 g) unsalted butter, melted and slightly cooled
- 1 large egg, lightly beaten
- 1½ teaspoons pure vanilla extract
For the blueberry filling:
- 4 cups (about 600 g) fresh or frozen blueberries
- ½ cup (100 g) granulated sugar
- 2 tablespoons lemon juice (fresh is best)
- 2 teaspoons lemon zest (about 1 medium lemon)
- 3 tablespoons cornstarch (or 4 tablespoons if using frozen berries)
- 1 teaspoon vanilla extract
- Pinch of salt
Ingredient tips & quick notes
- Flour: Regular unbleached all-purpose works well; if your flour is compacted, fluff it, then spoon and level for accuracy.
- Oats: Old-fashioned rolled oats give a nice chew; quick oats will work but give a slightly softer crumb.
- Butter: Use real butter here—this is what makes the buttery crumb crust so special. Salted butter is fine; just reduce the added salt to a pinch.
- Blueberries: Fresh blueberries give a brighter flavor, but frozen berries are great for a year-round fresh blueberry dessert feel. No need to thaw—just use extra cornstarch.
- Lemon: The lemon juice and zest keep the blueberry bar dessert from tasting flat; don’t skip them if you can help it.
Directions
You’ll build these blueberry crumb bars in layers: crust, filling, crumb topping. It sounds like a lot, but it moves fast.
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Preheat and prep the pan
Preheat your oven to 350°F (175°C). Line a 9×13-inch baking pan with parchment paper, leaving some overhang on the long sides so you can lift out the blueberry crumb squares later. Lightly coat the parchment and sides with cooking spray or a thin layer of butter. -
Mix the dry crust ingredients
In a large bowl, whisk together the flour, rolled oats, granulated sugar, brown sugar, baking powder, salt, and cinnamon. Break up any brown sugar clumps with your fingers. This mixture will become both the blueberry shortbread base and the crumb topping. -
Add the wet ingredients to form the crumb mixture
Pour the melted butter, beaten egg, and vanilla over the dry ingredients. Stir with a sturdy spoon or spatula until everything is evenly moistened. The mixture should look like coarse, sandy crumbs that clump a bit when pressed in your hand. -
Press in the base layer
Pour about ⅔ of the crumb mixture into the prepared pan. Use your hands or the bottom of a measuring cup to press it into an even, firm layer. This forms your buttery shortbread base. Press well, especially in the corners, so the bars hold together when sliced. -
Make the blueberry filling
In another bowl, combine the blueberries, sugar, lemon juice, lemon zest, cornstarch, vanilla, and a pinch of salt. Gently toss until the berries are coated and you don’t see any dry cornstarch. If using frozen berries, work quickly so they don’t release too much juice before baking. -
Spread the blueberry layer
Spoon the blueberry mixture evenly over the pressed crust. Make sure the berries and any juices are spread right into the corners, so every blueberry crumb bar has a jammy center. -
Add the crumb topping
Sprinkle the remaining crumb mixture evenly over the blueberries. You want some larger clumps and some smaller bits—that mix of texture is what makes a good blueberry crumb topping. Don’t press this layer too hard; just gently pat it so it sticks. -
Bake until golden and bubbly
Bake on the center rack for 40–50 minutes, or until the top is light golden brown and you can see the blueberry filling bubbling up around the edges. If your oven runs hot, start checking around 38–40 minutes. -
Cool completely (this part matters)
Place the pan on a cooling rack and let the bars cool completely—at least 2 hours. The blueberry filling will set as it cools. If you cut too soon, they’ll taste great but be a bit messy. For the cleanest slices, chill the pan in the fridge for 1–2 hours once it reaches room temperature. -
Slice and serve
Use the parchment overhang to lift the big slab of blueberry jam bars onto a cutting board. Cut into 16–24 blueberry crumb squares, depending on how generous you’re feeling. Serve at room temperature, or slightly warm with a scoop of vanilla ice cream.
Servings & Timing
- Yield: About 16 large bars or 20–24 smaller bars
- Prep Time: 20 minutes
- Bake Time: 40–50 minutes
- Cooling Time: 2–3 hours for clean slices
- Total Time: About 3–4 hours (mostly hands-off cooling time)
If you’re planning these for company, I like to bake the blueberry bar dessert in the morning or even the night before so they’re fully set and ready to go.
Variations
You know what? Once you’ve made this base blueberry crumb bar recipe, you can play with it like a canvas.
- Mixed Berry Crumb Bars – Swap in half raspberries or blackberries for a berry crumb bar recipe that’s pretty and tangy.
- Blueberry Jam Bars – Use 1½ to 2 cups good-quality blueberry jam instead of fresh fruit for an even easier blueberry jam bars version.
- Gluten-Free Blueberry Bars – Use a 1:1 gluten-free baking flour and certified gluten-free oats; bake time stays about the same.
- Lemon-Blueberry Crumb Bars – Add an extra tablespoon of lemon zest to the filling and drizzle with a simple lemon glaze after baking.
- Nutty Crumble Topping – Stir ½ cup chopped pecans or sliced almonds into the topping portion for extra crunch.
- Reduced Sugar Version – Cut the sugar in both the crust and filling by about ¼; the bars will be a bit less sweet but still lovely and fruity.
Storage & Reheating
A good blueberry bar dessert should hold up for a few days, and these do.
- Room temperature: Store sliced bars in an airtight container at cool room temperature for up to 2 days. Layer with parchment if stacking.
- Refrigerator: For longer keeping, refrigerate up to 5 days. The buttery crumb crust stays firm, and the blueberry layer stays fresh-tasting.
- Freezer: Freeze blueberry crumb squares on a baking sheet until solid, then transfer to a freezer bag or container. They keep well for up to 3 months.
To serve from frozen:
Let the bars thaw in the fridge overnight or at room temperature for about 30–45 minutes. You can warm individual bars in the microwave for about 10–15 seconds if you like them a bit soft and gooey.
There’s no real “reheating” needed, but if you want that just-baked vibe, you can place a few bars on a small baking sheet and warm them in a 300°F oven for 5–8 minutes.
For make-ahead gatherings, I often bake these summer blueberry bars one day ahead, chill them overnight, then slice and transfer to a serving platter the day of the event.
Notes
A few thoughts from many pans of blueberry crumb bars in my kitchen:
- Thickness of the base matters. If you like a firmer, cookie-like texture, press the base layer a bit more and keep the filling even. If you want extra crumble, hold back just a little more of the mixture for the topping.
- Cornstarch is your friend. It’s what turns the blueberries into a thick, jammy layer instead of blueberry soup. If your berries are very juicy, err on the higher side (another teaspoon won’t hurt).
- Cooling patience pays off. I know, it smells amazing, and everyone’s circling the kitchen. But these slice so much better when they’ve had time to set. I usually cut “taste tester” edges first—nobody complains.
- Sugar balance. Blueberries can vary a lot in sweetness. If your berries are very tart, add an extra tablespoon of sugar to the filling next time.
- Pan material. A light-colored metal pan tends to bake these more evenly. Glass works, but sometimes the edges brown faster; you might want to pull them out a few minutes earlier.
On a slightly nerdy note: search data shows that “easy blueberry crumb bars” and “fresh blueberry dessert” spike hard in July and August in the U.S.—which makes sense, because that’s peak blueberry season. If you’re freezing berries at their peak, you can keep that summer flavor going all year.
FAQs
Can I use frozen blueberries for this Blueberry Crumb Bars Recipe?
Yes, absolutely. Use them straight from the freezer, add an extra tablespoon of cornstarch, and bake until the filling is bubbling around the edges.
Do I need to thaw frozen blueberries first?
No, don’t thaw them. Thawed berries release more liquid and can make the bars too soft.
Can I make these bars dairy-free?
Yes. Use a good dairy-free butter substitute (the stick kind works better than the tub) and check that your sugar is vegan if needed.
How do I keep the crumb topping from getting soggy?
Make sure the bars bake long enough so the filling bubbles and the topping browns slightly. Cooling fully before covering also helps keep the crumb topping crisp.
Can I cut this recipe in half?
Yes. Halve all ingredients and bake in an 8×8-inch pan. The bake time will be close—start checking around 32–35 minutes.
Why did my blueberry filling seem runny?
Usually that means it either needed a bit more cornstarch or more cooling time. The filling thickens a lot as it cools.
Can I use other fruits instead of blueberries?
Yes. Strawberries, raspberries, blackberries, or a mix all work; just keep the total fruit around 4 cups and adjust cornstarch if the fruit is very juicy.
Can I add a glaze on top?
You can. A simple mix of powdered sugar and lemon juice makes these blueberry crumb bars look bakery-style and adds a little extra sweetness.
Conclusion
These blueberry crumb bars bring together everything I love in a dessert: a buttery crumb crust, a bright blueberry center, and a simple method that anyone can tackle on a busy weeknight. They’re just as welcome at a fancy brunch as they are on a paper plate at a backyard barbecue.
Give this Blueberry Crumb Bars Recipe a try and let me know how it goes—tell me if you made them with fresh berries, frozen ones, or turned them into mixed berry crumb bars. And if you love easy bar desserts, you might also enjoy trying my lemon bar recipe or a classic apple crumble bar next time.
Blueberry Crumb Bars (Buttery, Jammy & So Simple)
Ingredients
- 3 cups all-purpose flour 375 g; fluff, then spoon and level for accuracy
- 1 cup old-fashioned rolled oats 100 g; for a rustic crumble texture
- 1 cup granulated sugar 200 g; for the crust and topping
- 1/2 cup light brown sugar 100 g; packed
- 1 teaspoon baking powder
- 1/2 teaspoon fine sea salt
- 1 teaspoon ground cinnamon optional, but cozy with blueberries
- 1 cup unsalted butter 2 sticks / 226 g; melted and slightly cooled
- 1 large egg lightly beaten
- 1 1/2 teaspoons vanilla extract for the crumb crust and topping
- 4 cups blueberries about 600 g; fresh or frozen, do not thaw if frozen
- 1/2 cup granulated sugar 100 g; for the blueberry filling
- 2 tablespoons lemon juice fresh is best
- 2 teaspoons lemon zest about 1 medium lemon
- 3 tablespoons cornstarch use 4 tablespoons if using frozen berries, or more if berries are very juicy
- 1 teaspoon vanilla extract for the blueberry filling
- salt pinch, for the blueberry filling
Instructions
- Preheat your oven to 350°F (175°C). Line a 9×13-inch baking pan with parchment paper, leaving overhang on the long sides to lift the bars out later. Lightly coat the parchment and pan sides with cooking spray or a thin layer of butter.
- In a large bowl, whisk together the flour, rolled oats, 1 cup (200 g) granulated sugar, light brown sugar, baking powder, 1/2 teaspoon salt, and cinnamon (if using). Break up any clumps of brown sugar with your fingers. This mixture will serve as both the base crust and crumb topping.3 cups all-purpose flour, 1 cup old-fashioned rolled oats, 1 cup granulated sugar, 1/2 cup light brown sugar, 1 teaspoon baking powder, 1/2 teaspoon fine sea salt, 1 teaspoon ground cinnamon
- Pour the melted butter, beaten egg, and 1 1/2 teaspoons vanilla extract over the dry mixture. Stir with a sturdy spoon or spatula until everything is evenly moistened. The mixture should look like coarse, sandy crumbs that clump slightly when pressed in your hand.1 cup unsalted butter, 1 large egg, 1 1/2 teaspoons vanilla extract
- Transfer about two-thirds of the crumb mixture to the prepared pan. Use your hands or the bottom of a measuring cup to press it into a firm, even layer, making sure to press well into the corners. This forms the buttery shortbread-like base that will help the bars hold together when sliced.
- In another bowl, combine the blueberries, 1/2 cup (100 g) granulated sugar, lemon juice, lemon zest, cornstarch, 1 teaspoon vanilla extract, and a pinch of salt. Gently toss until the berries are evenly coated and no dry cornstarch remains. If using frozen berries, work quickly so they don’t release too much juice before baking.4 cups blueberries, 1/2 cup granulated sugar, 2 tablespoons lemon juice, 2 teaspoons lemon zest, 3 tablespoons cornstarch, 1 teaspoon vanilla extract, salt
- Spoon the blueberry filling evenly over the pressed crust, spreading the berries and their juices right into the corners so every bar has a jammy center.
- Sprinkle the remaining crumb mixture evenly over the blueberries. Leave some larger clumps and some smaller bits for varied texture. Gently pat the crumbs so they adhere, but do not press them firmly like the base.
- Bake on the center rack for 40–50 minutes, or until the top is light golden brown and the blueberry filling is bubbling around the edges. If your oven runs hot, start checking around 38–40 minutes.
- Transfer the pan to a cooling rack and let the bars cool completely, at least 2 hours. The blueberry layer will continue to thicken as it cools. For the cleanest slices, chill the pan in the refrigerator for 1–2 hours after it reaches room temperature.
- Use the parchment overhang to lift the slab of blueberry crumb bars onto a cutting board. Slice into about 16 large or up to 24 smaller bars. Serve at room temperature, or slightly warm with a scoop of vanilla ice cream if desired.
