These Blueberry Crumble Bars layer a jammy blueberry filling between a buttery, oat-forward crumble for a simple dessert that tastes like blueberry crisp in bar form. Made with fresh or frozen blueberries, they travel well and are ideal for summer gatherings, picnics, potlucks or any time you want an easy fruit dessert.
If you enjoy straightforward blueberry desserts, these Blueberry Crumble Bars should be on your summer baking list. They use pantry basics plus fresh or frozen blueberries and a crisp, buttery oat crumble that serves as both crust and topping. The result is a delightful contrast of soft, jammy fruit and a satisfying, crunchy topping.
Unlike loose crisps or cobblers, these bars hold their shape when sliced, so they’re perfect for transport and make-ahead serving. They are easy to adapt: swap coconut sugar for a deeper caramel note, use brown or granulated sugar instead, or make simple gluten-free and dairy-free substitutions.
Below you’ll find tips for avoiding soggy bars, how to work with frozen berries, and how to slice clean bars after they’ve fully set.
Why you’ll love this recipe
- A sweet, juicy blueberry filling brightened with fresh lemon zest and juice pairs perfectly with a hearty buttery oat crumble.
- Everything you love about a fruit crisp, reimagined as a portable bar that’s great for picnics, barbecues and potlucks.
- These bars are make-ahead friendly — they slice best once cooled and fully set.
- They’re simple to adapt to gluten-free and dairy-free diets with just a couple of ingredient swaps.
Recipe ingredients
This recipe uses simple pantry staples plus blueberries and lemon for a bright, fresh filling.
- Old fashioned rolled oats: Use rolled oats for chew and texture; quick oats can be used in a pinch but the texture will be softer.
- Flour: All-purpose works well. Substitute whole wheat or spelt for more fiber, or a 1:1 gluten-free flour or oat flour for a gluten-free version.
- Coconut sugar: Adds caramel-like depth without excessive sweetness. Packed light brown sugar or granulated sugar both work as alternatives.
- Cinnamon: A small amount adds warm flavor to the crumble.
- Butter: Unsalted butter creates a rich crumble; melt and stir into the dry ingredients. Replace with melted coconut oil for dairy-free bars.
- Blueberries: Fresh berries give the best texture and color, but frozen work fine if you thaw and blot excess moisture first to avoid a runny filling.
- Lemon zest and juice: Brighten and balance the sweetness without making the bars taste overtly lemony.
- Cornstarch: Two tablespoons help thicken the filling so the bars cut cleanly after cooling.
Quantities and the full ingredient list are included in the recipe section below.
How to make this recipe
These bars are straightforward: prepare the oat crumble, par-bake the crust, mix the blueberry filling, bake until bubbly and golden, then cool thoroughly. No fruit chopping required and the crumble comes together quickly.
Pro tip: Chill and cool the bars completely before slicing. The filling firms as it cools, which gives clean, sturdy slices.
Follow the recipe card below for detailed step-by-step instructions.
Tips for success
- Line the pan with parchment paper for easy removal and cleaner slices.
- Cool completely before cutting to prevent the filling from spilling out.
- Use old-fashioned rolled oats for the best texture; quick oats will soften more and yield a less substantial crumble.
- If the crumble browns too quickly, tent the pan loosely with foil for the last 15–20 minutes of baking.
- For an extra-crisp topping, chill the crumble mixture briefly before pressing into the pan.
Recipe FAQs
Yes. Frozen blueberries work well. Thaw them slightly and blot excess moisture with paper towels so the filling doesn’t become watery.
Yes. Replace the all-purpose flour with oat flour or a 1:1 gluten-free flour blend, and use certified gluten-free oats if needed.
Serving suggestions
Serve the bars as they are, or add a scoop of vanilla ice cream or a dollop of whipped cream. For a dairy-free option, serve with coconut whipped cream.
Storage and make-ahead tips
- Store leftovers covered at room temperature for up to 3 days, or refrigerate for up to one week.
- These bars freeze well. Wrap individual portions tightly and freeze for up to three months. Thaw overnight in the refrigerator or at room temperature before serving.
- Because they slice best after cooling, they’re an excellent make-ahead dessert for parties and gatherings.
More summer desserts you’ll love:
- Blueberry galette
- Cherry clafoutis
- Raspberry rhubarb crisp bars
- Peach blackberry cobbler
- Peach blueberry crisp
Did you try this recipe? If so, leave a review below and tag @flavorthemoments on social media to share your results.
Blueberry Crumble Bars
Ingredients
For the oatmeal crumble:
- 1 1/2 cups all-purpose flour (sub with oat flour for a gluten-free option)
- 1 1/2 cups old fashioned rolled oats
- 1/3 cup coconut sugar (or packed light brown sugar)
- 1 teaspoon ground cinnamon
- 1/4 teaspoon sea salt
- 3/4 cup unsalted butter, melted (or sub with melted coconut oil for dairy-free)
For the filling:
- 3 cups blueberries (about 1 1/2 pints)
- 1/2 cup coconut sugar (or your preferred granulated sugar)
- 1 tablespoon lemon zest
- 1 tablespoon fresh lemon juice
- 2 tablespoons cornstarch
Instructions
- Preheat the oven to 375°F. Line an 8×8″ baking dish with parchment paper or foil.
- In a medium bowl, combine the flour, rolled oats, 1/3 cup sugar, cinnamon and salt. Stir in the melted butter until the mixture is evenly moistened and holds together when pinched.
- Press two-thirds of the oat mixture firmly into the bottom of the prepared pan. Bake for 8–10 minutes, until lightly golden.
- Meanwhile, in a separate bowl combine the blueberries, 1/2 cup sugar, lemon zest, lemon juice and cornstarch. Toss gently to coat.
- Spread the blueberry mixture evenly over the par-baked crust. Sprinkle the remaining one-third of the crumble mixture over the top.
- Bake for 35–45 minutes, until the center is bubbly and the topping is golden. If the crumble is browning too quickly, loosely tent with foil after about 30 minutes.
- Cool the bars completely on a wire rack for at least 3 hours or overnight so the filling sets. Cut into bars and serve.
Notes
- Pro tip: Cooling is essential — the filling firms as it cools and yields neater slices.
- Frozen blueberries may be used; thaw slightly and blot excess moisture before mixing.
- Store leftovers at room temperature for up to 2–3 days or refrigerate for up to 1 week.
Nutrition (per bar)
Serving: 1 bar • Calories: 353 kcal • Carbohydrates: 48 g • Protein: 4 g • Fat: 17 g • Saturated Fat: 10 g • Polyunsaturated Fat: 6 g • Cholesterol: 43 mg • Sodium: 103 mg • Fiber: 3 g • Sugar: 23 g