Blueberry Oatmeal Crumble Bars

If you’re looking for a treat that’s fruity, buttery, and just the right amount of indulgent, these Blueberry Oatmeal Crumble Bars check every box. Bursting with juicy blueberries layered between a golden oat crumble that doubles as the base and the topping, these bars are a delicious fusion of pie and cookie. They’re easy to make, freezer-friendly, and perfect for breakfast, dessert, or anytime snacking.

The secret lies in the layered structure: a firm and chewy base made from oats, flour, and brown sugar gives the bars a hearty foundation, while the sweet-tart blueberry filling brightens each bite with fresh fruit flavor. A generous crumble topping adds a crispy, buttery finish that ties it all together. Whether you’re using fresh or frozen blueberries, this recipe is reliable, adaptable, and always a crowd-pleaser. Keep them on hand for potlucks, picnics, or just a simple afternoon treat with coffee.

Why You’ll Love This Recipe

1. Easy, One-Bowl Crust & Crumble – Uses the same mixture for both base and topping, minimizing prep.
2. Bursting with Blueberries – Fresh or frozen, this filling is naturally sweet and perfectly tart.
3. Great for Any Occasion – Suitable as breakfast, snack, or dessert.
4. Make-Ahead Friendly – Keeps well and freezes beautifully.
5. Better Than Store-Bought – Homemade with clean, simple ingredients and no preservatives.

Ingredients

For the Base & Crumble Topping

• All-purpose flour
• Old-fashioned oats (large flake)
• Granulated sugar
• Brown sugar (packed)
• Cinnamon
• Salt
• Unsalted butter (melted)
• Large egg yolk

For the Blueberry Layer

• Blueberries (fresh or frozen)
• Lemon juice (freshly squeezed)
• Granulated sugar
• Cornstarch

Variations

• Use Different Berries: Try raspberries, blackberries, or a mix of berries.
• Add Nuts: Mix chopped almonds or walnuts into the crumble for added texture.
• Make It Gluten-Free: Use a 1:1 gluten-free flour blend and certified gluten-free oats.
• Lemon Zest Boost: Add zest to the filling for a more pronounced citrus note.
• Top with Icing: Drizzle with a lemon glaze or vanilla icing once cooled.

How to Make the Recipe

Step 1

Preheat your oven to 350°F (175°C). Line an 8×8-inch baking pan with parchment paper or lightly grease it.

Step 2

In a large bowl, mix together flour, oats, granulated sugar, brown sugar, cinnamon, and salt.

Step 3

Add melted butter and egg yolk to the dry mixture. Stir until crumbly and well combined.

Step 4

Press about two-thirds of the oat mixture firmly into the bottom of the prepared pan to form the base.

Step 5

In a separate bowl, toss blueberries with lemon juice, sugar, and cornstarch until evenly coated.

Step 6

Spread the blueberry mixture over the oat base in an even layer.

Step 7

Sprinkle the remaining oat mixture over the blueberries to form the crumble topping.

Step 8

Bake for 35–40 minutes (add 5–10 minutes if using frozen berries), until the top is golden brown and bubbling.

Step 9

Cool completely in the pan before slicing into bars.

Tips for Making the Recipe

• Use parchment paper for easy removal and clean slicing.
• Press the base firmly to avoid a crumbly bottom layer.
• Don’t overbake—the bars continue to set as they cool.
• Use fresh lemon juice for the best flavor in the fruit filling.
• Let bars cool fully before cutting to prevent falling apart.

How to Serve

Serve chilled or at room temperature. Perfect with a cup of tea or coffee, or topped with a scoop of vanilla ice cream for dessert. They also make a sweet addition to brunch spreads or lunchboxes.

Make Ahead and Storage

Storing Leftovers

Store in an airtight container at room temperature for up to 2 days or in the refrigerator for up to 5 days.

Freezing

Freeze fully cooled bars between layers of parchment paper in a sealed container for up to 2 months. Thaw in the refrigerator overnight before serving.

Reheating

These bars are best enjoyed at room temperature or slightly chilled. You can warm them in the microwave for 10–15 seconds for a soft, just-baked texture.

FAQs

1. Can I use frozen blueberries?

Yes, just don’t thaw them first and extend baking time by 5–10 minutes.

2. Can I make these bars gluten-free?

Absolutely—just use a gluten-free flour blend and certified gluten-free oats.

3. How do I prevent a soggy base?

Make sure to press the base firmly and bake until golden to avoid sogginess.

4. Can I double the recipe?

Yes! Use a 9×13-inch pan and increase baking time slightly.

5. Do I need to cook the blueberry filling first?

No, it cooks perfectly in the oven with the bars.

6. Can I substitute quick oats?

Old-fashioned oats give better texture. Quick oats may result in a softer, less chewy bar.

7. Can I add lemon zest to the filling?

Yes—it adds a bright, citrusy note that complements the blueberries.

8. What’s the best way to cut clean bars?

Chill completely, then use a sharp knife wiped clean between cuts.

9. Are these bars overly sweet?

They strike a nice balance. Reduce the sugar slightly if you prefer a more tart flavor.

10. Can I make these dairy-free?

Yes, substitute the butter with a dairy-free alternative like coconut oil or vegan butter.

Conclusion

Blueberry Oatmeal Crumble Bars are the ultimate easy-bake treat—wholesome, fruity, and satisfying without being overly rich. With their crumbly oat crust, fresh berry center, and golden topping, they offer everything you love about pie and cookies in one delicious square. Ideal for sharing, storing, or savoring solo, these bars are as flexible as they are flavorful. Make a batch, and watch them disappear!

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