Wednesday, May 28, 2025 · 99 Comments

Lemon Blueberry Crumble Bars (with Oat Streusel)

These lemon blueberry crumble bars are packed with juicy berries, creamy lemon filling, and a buttery oat streusel that’s both the crust and topping. I like how the tart lemon cuts through the sweetness for that sweet-tart bite I’m always after.

The Sweet-Tart Magic of Lemon Blueberry Bars with Oat Streusel

These lemon blueberry crumble bars are one of my favorite ways to use up fresh blueberries. They’ve got a creamy lemon filling made with sweetened condensed milk, a soft oat-based crust, and a golden crumble on top. Everything bakes together into a bar that’s sweet, tart, and just the right amount of buttery.

I like these because they’re easier than making a traditional lemon bar, but you still get that lemony punch. The filling isn’t too tart or too sweet, and the oat streusel adds a texture you don’t get in smooth lemon bars. Add a layer of juicy blueberries and you’ve got something with a little more going on.

These work for potlucks, summer get-togethers, or just keeping in the fridge for an easy treat. The lemon and blueberry combo never misses, and I’ve made sure this recipe’s about as foolproof as it gets.

What Makes These Lemon Blueberry Bars Stand Out

I made the oat streusel pull double duty here—it’s both the crust and the topping, and the combo of flour and oats gives it that perfect crumbly texture with a little chew. The filling is what sets these apart though: it’s creamy, smooth, and lemony without being too tart or too sweet. I use sweetened condensed milk and egg yolk to get that rich, custardy layer that’s nothing like the stiff or jello-like lemon bars out there.

The blueberries bake right into it and give you those juicy bursts that work so well with the lemon. Even with all the layers, this recipe stays simple—no special tricks, just a bar that works every time.

These aren’t your usual lemon bars. Instead of a firm, jelled layer and shortbread crust, this version uses a creamy filling and a buttery oat topping. The blueberries make it feel more like a cross between a lemon bar and a fruit crisp.

Why You’ll Love This Recipe

Lemon and blueberry are the ultimate food marriage.
Made with simple pantry staples.
Oat streusel on top and bottom means max flavor, minimal effort.

What You’ll Need to Make These Bars

This recipe uses simple ingredients that come together to make something really good. (You can take a peek at all necessary ingredients in the photo below.)

All-purpose flour – forms the base and gives the bars structure.
Old-fashioned rolled oats – not quick oats; these hold up well and make the streusel chewy.
Light brown sugar – sweetens the crust and topping and helps them brown.
Baking powder – gives the crust a little lift.
Table salt – brings out the lemon and balances the sweetness.
Unsalted butter – soft, not melted, so it blends into the dry mix just right.
Egg – the yolk makes the filling smooth, the white helps bind the crust.
Sweetened condensed milk – makes the lemon layer creamy and sweet without being too much.
Lemon zest and juice – fresh lemon gives the filling real flavor and just the right amount of tartness.
Blueberries – fresh and room temp so they bake evenly and keep the filling smooth.

If you’ve got extra blueberries to use up, try my blueberry-lime pound cake or cornmeal-blueberry drop scones—they both play off the blueberry-citrus pairing in different ways.

How to Make Lemon Blueberry Crumble Bars

Find the complete printable recipe with measurements in the recipe card at the bottom of the post.

Step One (make the base and topping)
Grab a big bowl and mix the flour, oats, brown sugar, baking powder, and salt. Add the softened butter and use your hands to work it in until the whole thing looks crumbly. Scoop out 2 cups and set that aside for the topping.
Step Two (add the egg white)
Take the rest of the crumb mixture and stir in the egg white. I usually use a wooden spoon, but anything works as long as it’s mixed well.
Step Three (press the crust)
Line a 9×13 metal pan with foil and leave some extra hanging over the sides so you can lift the bars out later. Lightly butter the foil, then press in the egg white mixture to make an even crust. Bake it at 350°F for about 10 to 12 minutes. (You can see the pressed in oat crust in the photo below.)
Step Four (make the lemon filling)
While the crust bakes, whisk together the sweetened condensed milk, lemon juice, lemon zest, and the egg yolk. Let it sit for five minutes—it’ll start to thicken up a bit.
Step Five (assemble the filling layer)
Once the crust is out of the oven, scatter the blueberries evenly over the hot crust. Spoon the lemon filling over the berries and gently spread it out. Don’t mash the blueberries—just move the filling around enough to cover everything.
Step Six (partial bake)
Pop the pan back in the oven for 8 minutes. The filling will start to set up a little.
Step Seven (add the crumble)
Take that topping you saved earlier and pinch it into little clumps as you sprinkle it over the lemon-blueberry layer. It doesn’t have to be perfect—just make sure it’s spread out pretty evenly.
Step Eight (final bake)
Bake for about 30 minutes, until the topping is golden and you see the filling bubbling around the edges.
Step Nine (cool and cut)
Let the bars cool in the pan for an hour, then use the foil overhang to lift them out and let them finish cooling on a rack. Once they’re fully cool, peel off the foil and cut into bars. I keep them in the fridge and warm one up in the microwave when I want a soft, creamy bar.

Tips for Making Lemon Blueberry Crumble Bars

This recipe’s pretty forgiving, but there are a few things that help it turn out just right.

Let your butter and egg come to room temp before starting.
Same goes for the blueberries—if they’re cold, they can mess with how the filling bakes and sets.
Don’t skip pre-baking the crust. It helps keep the bottom layer firm so it doesn’t get soggy.
Use a metal pan, not glass or ceramic. It helps the crust bake evenly and avoids overbaking the edges while the center sets.
Let the bars cool most of the way before lifting them out of the pan, and don’t slice them until they’re fully cooled.
If you want clean cuts and that creamy filling to hold its shape, cooling completely is key.
These are great to make ahead—just store them in the fridge once cooled, and slice when you’re ready to serve.

Storing and Freezing These Bars

Once the bars are completely cool, slice them and store what you’re not eating right away.

Keep them in the fridge in an airtight container for up to a week.
I like to microwave one for a few seconds if I want it warm again.
To freeze, wrap each bar in plastic wrap and stash them in a sealed container. They’ll keep well for up to 3 months.

If you’re working with fresh blueberries and want to keep extras in top shape for baking or snacking, these tips from the U.S. Highbush Blueberry Council are worth checking out.

Your Lemon Blueberry Bar Questions, Answered (FAQs)

What does the egg white in the crust do? It helps hold the crust together so it doesn’t crumble apart when sliced.
Can I use frozen blueberries? I don’t recommend it. Frozen berries tend to release too much moisture and can seize the filling, which throws off the texture. Fresh, room-temp blueberries work best here.
Why didn’t my lemon filling set? It could be slightly underbaked, or the ratios might be off. Be sure to follow the ingredient amounts closely and give the filling a few minutes to thicken before pouring it over the crust.
Can I make these gluten-free? I haven’t tested a version without gluten, but a 1:1 gluten-free flour blend and certified gluten-free oats could be worth trying if you’re comfortable experimenting.
How are these different from traditional lemon bars? They’re creamier, softer, and have a buttery oat streusel instead of shortbread. The blueberries also add a fruit layer you don’t get in the classic kind.
Can I use bottled lemon juice? You really need fresh lemon juice for the right flavor—and since you need the zest too, you’ll want to start with whole lemons anyway.
What’s the best way to cut clean bars? Wait until they’re fully cool, then use a sharp knife and clean it between cuts. You can chill them first if you want super neat slices.

How to Serve These Bars

These are great chilled straight from the fridge, or warmed slightly in the microwave. I’ve brought them to potlucks, added them to dessert boards, and even topped them with a little whipped cream when I wanted something extra.

More Sweet Treats Worth Baking

If these lemon blueberry crumble bars hit the spot, you might be looking for your next easy-to-bake dessert. Here are some of my other favorite bar recipes, along with more ways to enjoy those juicy blueberries.

Lime Bars – All the flavor of key lime pie, no crust needed.
Reese’s Pieces Bars – Chewy, soft, and full of peanut butter crunch.
No-Bake Strawberry Cheesecake Bars – Cold, creamy, and layered with strawberries.
Blueberry Lemon Cake – Buttermilk cake with fresh blueberries and lemon throughout.
Blueberry Cobbler with a Secret Spice Twist – Juicy and warm with an unexpected kick.
Blueberry Dump Cake with Pie Filling and Fresh Berries – yellow cake mix and golden crust.

And if you’re looking for even more ways to put fresh blueberries to use, I pulled together 18 ways to use blueberries this summer—a mix of sweet, savory, and everything in between.

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Lemon Blueberry Crumble Bars (with Oat Streusel)

Print Recipe

5 from 13 votes

Lemon Blueberry Crumble Bars (with Oat Streusel)

These lemon blueberry crumble bars are layered with creamy lemon filling, juicy blueberries, and a buttery oat streusel that forms both the crust and topping. This easy dessert skips the cream cheese and goes all in on real lemon flavor and fresh fruit. Slice them clean once cooled and keep them chilled for the perfect sweet-tart bar.

Prep Time20

Cook Time50

Cooling1

Total Time2 10

Course: Dessert

Cuisine: American

Keyword: blueberry lemon dessert, creamy lemon filling, lemon blueberry bars, lemon blueberry crumble bars, oat streusel bars

Servings: bars

Calories: 228kcal

Author: Cathy Pollak

Equipment

measuring cups and spoons For ingredient measuring accuracy.
mixing bowls For combining the dry ingredients and preparing the filling.
9 x 13 metal baking pan (23x33 cm). Helps the crust bake evenly and prevents sogginess.
aluminum foil or parchment. For lining the metal baking pan.
rubber spatula For spreading the lemon filling over the blueberries.
whisk To blend the lemon filling smoothly.

Ingredients

Crust & Crumble Topping:

3 cups (375 g) all-purpose flour
1½ cups (135 g) old-fashioned rolled oats (not quick oats)
1⅓ cups (267 g) packed light brown sugar
1 tsp. (4 g) baking powder
1 tsp. (6 g) table salt
1 cup (227 g) + more for the pan unsalted butter cut into cubes and at room temp
1 large egg, separted (1 egg white + 1 egg yolk)

Filling:

1 (14 oz./396 g) can sweetened condensed milk
2 tsp. (4 g) lemon zest (to get 2 tsp. you will need one large or 2 smaller lemons)
½ cup (120 ml) fresh lemon juice
2½ cups (350 g) fresh blueberries room temp

Instructions

Preheat oven to 350°F (175°C).
In a large bowl, mix the flour, oats, brown sugar, baking powder, and salt.
3 cups (375 g) all-purpose flour, 1½ cups (135 g) old-fashioned rolled oats, 1⅓ cups (267 g) packed light brown sugar, 1 tsp. (6 g) table salt, 1 tsp. (4 g) baking powder
Add the butter and work it in with your fingers until crumbly. Set aside 2 cups of this mixture for the topping.
1 cup (227 g) + more for the pan unsalted butter
Mix the egg white into the remaining crumb mixture until well blended.
1 large egg, separted
Line a 9x13-inch (23x33 cm) metal baking pan with foil, leaving a 1-inch overhang on the sides. Lightly butter the foil.
Press the egg white crumb mixture into the pan to form the crust. Bake for 10–12 minutes.
While the crust bakes, whisk the sweetened condensed milk, lemon zest, lemon juice, and egg yolk in a bowl. Let sit 5 minutes.
1 (14 oz./396 g) can sweetened condensed milk, 2 tsp. (4 g) lemon zest, ½ cup (120 ml) fresh lemon juice
Scatter the blueberries evenly over the hot crust. Pour the lemon mixture over them and gently spread it without crushing the berries.
2½ cups (350 g) fresh blueberries
Bake for 8 minutes
Crumble the reserved topping over the filling, pressing it into small clumps as you go.
Bake for 30 minutes more, until the top is golden and the filling bubbles around the edges.
Let cool in the pan for about 1 hour.
Use the foil overhang to lift the bars out and cool fully on a wire rack.
Once cool, remove the foil and slice into 24 bars. Store in the fridge.

Notes

Don’t use frozen blueberries—they can release too much water and seize the lemon filling.
Letting the filling rest for 5 minutes before baking helps it thicken slightly.
Cool completely before cutting for clean bars with set layers.
To freeze: wrap each bar individually and store in an airtight container for up to 3 months.
You’ll need fresh lemons for the zest, so go with fresh juice too—bottled just isn’t the same.

For the best results when making these lemon blueberry crumble bars, check out the full post. It includes extra notes, tips, and frequently asked questions that aren't listed in the recipe card — like how to make it dairy-free, gluten-free, or ideas for simple ingredient swaps.

Nutrition information is an estimate and will vary based on the brands and products you use.

© noblepig.com. All content and photographs are copyright protected. Sharing a link to this recipe is encouraged and appreciated, but copying and/or pasting the full recipe to social media or other websites is strictly prohibited.

Nutrition

Nutrition Facts

Lemon Blueberry Crumble Bars (with Oat Streusel)

Amount Per Serving (70 g)

Calories 228 Calories from Fat 81

% Daily Value*

Fat 9g14%

Saturated Fat 5g31%

Polyunsaturated Fat 0.5g

Monounsaturated Fat 2.5g

Cholesterol 28mg9%

Sodium 125mg5%

Potassium 95mg3%

Carbohydrates 34g11%

Fiber 1g4%

Sugar 19g21%

Protein 3g6%

Vitamin A 275IU6%

Vitamin C 2mg2%

Calcium 65mg7%

Iron 1mg6%

* Percent Daily Values are based on a 2000 calorie diet.

Have you made these Lemon Blueberry Crumble Bars? I’d love to hear how they turned out — leave a comment below and let me know.

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Comments

5 from 13 votes