These blueberry oatmeal crumble bars are bursting with juicy blueberries and filled with crunchy oatmeal crumble. They can be made with fresh or frozen blueberries, and the oatmeal mixture doubles as the base and crumble topping. Delicious for dessert with a scoop of ice cream – you’ll also love the leftovers for an extra special breakfast.
**This recipe was updated August 16, 2020 with new photos, recipe tips, and storage instructions**
My blueberry crisp bars are always a huge hit over the spring and summer months. They have a buttery shortbread base, a layer of fresh blueberries, and a crunchy crumb topping.
But I wanted to make a version with oatmeal crumble. Because I’m pretty sure that if there’s oatmeal – then it’s breakfast approved. And because adding oatmeal creates even more delicious crunchy crumble with lots of texture. And that’s always a good thing.
Enter – blueberry oatmeal crumble bars. They have a crunchy oatmeal cookie base, a layer of extra juicy blueberries, and cinnamon oatmeal crumble on top. There’s so much texture, and the oatmeal really holds up to the juicy berries.
I’ve definitely had these for breakfast (they can’t be that much worse than sugary cereals), or with a scoop of vanilla ice cream for dessert. And for whatever reason, I think they’re completely delicious cold and right from the fridge.
Blueberry Oatmeal Crumble Bar Recipe
One of the best parts of this recipe is that we’re using the same mixture for the oatmeal cookie base and the crumble topping. First, we whisk together flour, oats, sugar, and a little cinnamon. Then melted butter and 1 egg yolk are stirred in. Make sure to use old-fashioned or large flake oats. Quick oats & instant oats have less texture and behave more like flour in recipes. So I don’t recommend the substitution in this recipe.
About 3/4 cup to 1 cup is reserved for the crumble topping, then the rest of the mixture is pressed into the bottom of the pan to form the oatmeal base.
For the blueberry filling, we’re using blueberries, lemon juice, a little sugar and some cornstarch. You can use fresh or frozen berries, however, the bake time will be a little longer if using frozen berries. The lemon juice helps to soften the berries and bring out the flavor and the cornstarch thickens the mixture.
Then spoon the blueberry mixture on top of the bottom oatmeal layer. You want the entire oatmeal base layer covered with berries. Then crumble the remaining oatmeal mixture (with a little extra brown sugar mixed in) on top of the berries. From there, the bars are ready to bake.
You can see the process of assembling the bars below, and what they look like once they come out of the oven:
These blueberry oatmeal crumble bars are full of texture and packed with juicy berries. I love making these for dessert and then having the leftovers for breakfast.
For more fruit crumble bars – try these other favorites:
Or for more blueberry recipes, try these other favorites:
Blueberry Oatmeal Crumble Bars
- 8x8 inch (20x20 cm) baking pan
For the Base & Crumble Topping
- 1 cup all-purpose flour*
- 3/4 cup old-fashioned oats* AKA large flake oats (not quick oats or instant oats)
- 1/2 cup granulated sugar
- 1/4 cup packed brown sugar
- 1/2 teaspoon cinnamon
- 1/4 teaspoon salt
- 1/2 cup unsalted butter melted
- 1 large egg yolk discard the egg white
- 1 tablespoon packed brown sugar
For the Blueberry Layer
- 2 cup blueberries* fresh or frozen - see baking time adjustment if using frozen
- 1 tablespoons lemon juice freshly squeezed
- 1/4 cup granulated sugar
- 2 teaspoons cornstarch
- Preheat the oven to 350F degrees. Line an 8x8 baking pan with parchment paper leaving an overhang around the edges. Or line with aluminium foil leaving an overhang around the edges and grease with non-stick cooking spray.
Oatmeal Base & Topping
- In a medium bowl whisk together the flour, oatmeal, granulated sugar, 1/4 cup brown sugar, cinnamon, and salt. Gently stir in the melted butter & egg yolk. Note: if the mixture feels very buttery, optionally add in 1 extra tablespoon of flour.
- Remove about 1 cup (not packed) of the mixture and mix with the additional 1 tablespoon of brown sugar.
- Press the remaining mixture into the bottom of the prepared pan.
- In a medium bowl stir together the berries, sugar, lemon juice and cornstarch until the berries are coated.
Assembly and Baking
- Spoon the berry mixture over top of of the oatmeal base.
- Crumble the reserved oatmeal mixture over top of the blueberry layer. I like to form crumbles by squeezing it in my fist.
- Bake in the preheated oven for about 45-55 minutes or until you see the blueberries bubbling and the top crumble turning golden brown. If you used frozen berries, the bake time will be closer to 50-60 minutes.
- Cool the bars fully (while keeping them in the pan) until they're room temperature (at least 3 hours) before slicing.
- To slice the bars, lift them out of the pan using the overhang of the parchment paper/aluminum foil. Place on a cutting board and slice with a large, sharp knife.
- Bars can be served cold from the fridge, room temperature, or warmed up in the microwave. Optionally, add a scoop of ice cream on top of each.
- Make sure to use old-fashioned oats, also known as large rolled oats. Do not use quick oats, instant oats or steel-cut oats for this recipe.
- If the oatmeal layer seems very damp/buttery, optionally add in 1-2 additional tablespoons of flour as needed.
- This recipe is designed for an 8x8 inch (20x20 cm) pan. There is not quite enough batter for a 9x9 inch pan - therefore, I do not recommend using that pan size.
- To double the recipe, double all the ingredients and bake in a 9x13 inch pan. The bake time will be about the same.
- Nutrition information is based on 1 bar, assuming the recipe is sliced into 9 equal pieces. It is an estimate only.
- Store bars in an airtight container in the fridge for up to 4 days. Bars can be frozen for up to 2 months and thawed in the fridge.