I’ve made these blueberry crumble bars on slow Sunday mornings when fresh berries are plentiful and we need something simple to wow a crowd. They’re a cross between a shortbread base and a fruit-filled crumble — buttery, tangy from a splash of lime, and easy enough for a weeknight dessert or to pack for a picnic.

Why you’ll love this dish

These bars hit the sweet spot when you want dessert that feels homemade without hours of fuss. A tender, sandy crumb forms a sturdy base and a crunchy top while the blueberries become a jammy filling that never needs added pectin. They’re perfect for brunch, a potluck, or when you want to use up a pint of berries.

“The perfect balance of buttery crust and bursting blueberry filling — easy to make and disappears fast.” — a neighborly taste-test

If you enjoy tray-bakes that travel well, you might also like caramel apple cheesecake bars, another crowd-pleasing option.

How this recipe comes together

Make a coarse, sandy crumble dough by rubbing cold butter into flour, sugar, baking powder and salt, then bind it lightly with an egg.
Press half the crumb into a 9×9″ pan to form a shortbread-like base.
Toss blueberries with lime, sugar, and cornstarch so they release juices and thicken while baking.
Layer berries over the crust, sprinkle the remaining crumbs on top, and bake until the fruit bubbles and the top is golden.
Cool completely so the filling sets — refrigeration overnight makes the cleanest slices.

This quick overview helps you mentally organize the work: dough, press, fruit, top, bake, cool.

What you’ll need

1 1/2 cups all-purpose flour
1/2 teaspoon baking powder
1/8 teaspoon salt
1 stick (8 tablespoons) cold salted butter, cubed
1 large egg
1 pint (about 2 cups) blueberries
3/4 cup sugar (divided: 1/2 cup + 1/4 cup)
1/8 cup lime juice (about 2 tablespoons)
2 teaspoons cornstarch

Notes and simple substitutions:

For a less sweet bar, cut total sugar by 1–2 tablespoons.
Use unsalted butter and add a pinch more salt if preferred.
Lemon juice can substitute for lime if that’s what you have on hand.

Step-by-step instructions

Preheat the oven to 375°F. Butter a 9×9″ glass baking dish and set it aside.
In a mixing bowl, whisk together 1 1/2 cups flour, 1/2 cup sugar, 1/2 tsp baking powder and 1/8 tsp salt.
Add the cubed cold butter and the egg. Use a fork, your fingertips, or a pastry cutter to work the butter into the dry ingredients until the mixture resembles a coarse crumble. Small pea-sized bits of butter are fine.
Press half of the crumb mixture firmly into the bottom of the prepared baking dish to make the base. Create an even layer so the filling has solid support.
In another bowl, whisk 1/8 cup lime juice with 1/4 cup sugar and 2 tsp cornstarch until smooth. Add the blueberries and gently toss until evenly coated.
Spread the blueberry mixture evenly over the pressed crust.
Scatter the remaining crumb mixture over the blueberries — it should nearly cover the fruit but leave some berry peeking through.
Bake for 45–50 minutes, until the blueberries are bubbly and the top is golden brown. Rotate the pan once halfway through if your oven bakes unevenly.
Cool completely before slicing. An hour at room temperature may work; chilling overnight produces the cleanest bars.

Best ways to enjoy it

Serve bars at room temperature or slightly chilled. Top slices with:

A scoop of vanilla ice cream for a classic warm-and-cold contrast.
A dollop of lightly sweetened whipped cream and a few fresh berries for brunch.
A drizzle of crème fraîche or lemon glaze for extra brightness.

For a picnic or bake sale, cut into squares and place on parchment — they hold up well. And if you want another great tray-bake for gatherings, try caramel apple cheesecake bars for a fall twist.

How to store & freeze

Room temperature: Keep airtight for up to 2 days. Bars soften over time but remain tasty.
Refrigerator: Store in an airtight container for 4–5 days. Chilling firms the filling and makes slicing neater.
Freezer: Wrap individual squares in plastic and freeze in a sealed bag for up to 2 months. Thaw in the refrigerator or at room temperature.
To reheat: Warm a slice in a low oven (300°F) for 8–10 minutes, or microwave for 12–20 seconds if serving with ice cream.

Practice basic food safety: cool completely before refrigerating and don’t keep perishable desserts at room temperature longer than 2 hours.

Pro chef tips

Keep the butter cold: it creates a flakier, crumblier texture. If your kitchen is warm, chill the bowl or pop the crumb topping into the fridge for 10 minutes before sprinkling.
Don’t overwork the dough: once you add the egg, mix just enough to distribute the butter. Overmixing develops gluten and makes the crumb tougher.
Use fresh or thawed, drained frozen blueberries. If using frozen, toss them with the cornstarch mixture while still frozen — this helps absorb excess juice.
Press the base firmly so the filling doesn’t seep underneath. A measuring cup makes a great tamper for an even layer.
If the top is browning too fast, tent with foil for the last 10–15 minutes.

If you want a richer crumble, add 1/3 cup old-fashioned oats and 1/4 cup chopped nuts to the crumb mix for texture. For another easy fruit bar to rotate into your repertoire, check out caramel apple cheesecake bars.

Creative twists

Lemon-Blueberry: Swap lime for lemon and add 1 tsp lemon zest to the crumb for extra brightness.
Streusel Top: Stir 1/4 cup brown sugar and 1/3 cup oats into the remaining crumb for a crunchy streusel.
Gluten-free: Use a 1:1 gluten-free flour blend and reduce liquid slightly if the dough feels too wet.
Vegan: Replace butter with cold vegan butter and the egg with a flax “egg” (1 tbsp ground flax + 3 tbsp water, chilled). Texture will be slightly different but still delicious.
Mixed Berry: Use a pint of mixed berries (blueberries, raspberries) — increase cornstarch to 1 tbsp for extra thickening.

Common questions

Q: Can I use frozen blueberries?

A: Yes. No need to thaw. Toss them frozen with the lime, sugar and cornstarch; frozen berries release more juice, so the cornstarch helps. Expect a slightly more jammy filling.

Q: Why lime juice instead of lemon?

A: Lime gives a slightly sharper, brighter acidity that pairs beautifully with blueberries. Lemon is a fine substitute if you prefer its flavor.

Q: How long before serving should I cut the bars?

A: Cool completely before cutting. One hour at room temperature is okay, but chilling overnight makes the cleanest, firmest slices.

Q: Can I make this ahead?

A: Yes — bake, cool, then refrigerate for up to 4 days or freeze individual slices for longer storage. Reheat briefly if you prefer them warm.

Q: My filling was runny—what went wrong?

A: Possible causes: underbaked (not hot enough or not long enough), too many soft berries, or too little cornstarch. Next time add an extra 1/2–1 teaspoon cornstarch for very juicy berries.

Conclusion

These blueberry crumble bars are an approachable, reliable dessert that highlights fresh berries and buttery crumbs. For a classic take on a similar treat, consult the Blueberry Crumb Bars Recipe which covers variations and reader tips. For a slightly more refined, step-by-step plated approach, see the recipe at Blueberry Bars with Crumble Topping – Cooking Classy for inspiration.