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.

Course Dessert

Cuisine American

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

Prep Time 20

Cook Time 50

Cooling 1

Total Time 2 10

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.

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