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 ¾ 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.
Recipe Video
For more fruit crumble bars – try these other favorites:
Or for more blueberry recipes, try these other favorites:
Blueberry Oatmeal Crumble Bars
Equipment
- 8x8 inch (20x20 cm) baking pan
Ingredients
For the Base & Crumble Topping
- 1 cup all-purpose flour*
- ¾ cup old-fashioned oats* AKA large flake oats (not quick oats or instant oats)
- ½ cup granulated sugar
- ¼ cup packed brown sugar
- ½ teaspoon cinnamon
- ¼ teaspoon salt
- ½ 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
- ¼ cup granulated sugar
- 2 teaspoons cornstarch
Instructions
- 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, ¼ 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.
Blueberry Layer
- 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.
Notes
- 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.
Nutrition
Lindsay | With Salt and Pepper
YUM!!!! I love fruit bars…and oatmeal on top takes it to another level 🙂
Kimberly
I made this dish about a week ago, left out the cinnamon (just not a personal fan with blueberries), doubled the recipe for enough to fit a 13 x 9 pan. My kids demolished these in under 24 hours. My son said it tasted like a blueberry cobbler in a bar. So easy, so fresh, so good.
Fiona
Thanks so much! Sounds like it was a good thing you doubled the recipe!
Vanessa
What happens if you use instant oats instead?
Fiona
Because instant oats are very fine, they behave more like flour – which means the bars can end up becoming too dry and crumbly.
Diane
Thank you! I was wondering about doubling😊
Norma Jean
Simply delicious! Thanks for sharing!
Patty
I made these last night and they were a big hit at work. In fact, I have never before received so many compliments! I need to mention how simple the recipe is. It only took me 5 minutes. I used frozen blueberries and my berries made a little juice which was absolutely perfect.
Fiona
I’m so glad everyone loved the bars! Thanks for reporting back
Sandy
This recipe worked great as an allergy friendly dessert. I used Bob’s Red Mill gluten free baking mix instead of the flour and coconut oil instead of the butter. My grandchildren loved them. Since my 8×8 pan was being used, I used my 11×7 pan and it worked out just fine. I will definitely be making this one again.
Fiona
Thanks so much for reporting back! My brother-in-law has quite a few food allergies – so I’ll have to try making the recipe with your substitutions for him 🙂
Debra
I made it! delicious1 I also doubled the recipe. Thank you!
For some reason the print button does not work???
Fiona
I’m so glad you loved the recipe! And thanks for letting me know about the print button 🙂
Diane
Hi the only issue I had with this recipe is that it was far too sweet, esp for breakfast. I cut the sugar down a bit but still found it too much. I’m going to try this recipe with half the amount of sugar especially if the blueberries are sweet and see what happens.
Thanks for sharing this.
Christopher Mohs
This recipe was so easy and delicious! Consequently it served as inspiration for a new recipe we whipped up this weekend for our blog. https://pumpernickelandrye.com/peach-graham-crumble-bars/ We were happy to give you a shoutout. Keep up the great work!
Fiona
Thanks so much for reporting back and the shout out! Those peach bars look amazing – Pinned!
Rachel
I made these today and they are delicious! I was a little worried after it was mixed up because I realised I did use quick oats (as that’s what I had in the house), and my frozen blueberries looked like they were forgotten in the freezer for years (but I used them anyway).
These squares smelled so delicious while baking, and even more so after I took them out and waited(excruciatingly) for them to cool completely before cutting. I just had one with coffee and it was scrumptious! It tasted like something you’d get a nice coffee shop. I’m not sure how healthy they are, but that won’t stop me from making them again (and maybe having seconds right now).
Anna
I’m not a blueberry fan. Can you use different kinds of fruits? What would you recommend?
Fiona
You could replace the blueberries with raspberries, blackberries or a mixed berries. I also have this recipe for Apple Oatmeal Bars: https://www.justsotasty.com/apple-oatmeal-crumb-bars/and this recipe for strawberry crumb bars: https://www.justsotasty.com/strawberry-crumb-bars/
Beth
We made these yesterday! Let’s just say they are gone today! Thank you, they were delish!!!!