Blueberry Oatmeal Bars — These bars are buttery and packed with blueberry flavor! They take just 10 minutes of prep and then go straight into the oven. So easy to make, and a crowd pleaser every time!
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Best Ever Blueberry Crumble Bars
This blueberry crumble bars recipe is an easy, one bowl, no mixer recipe that takes just minutes to make. I adapted the recipe from my Blueberry Pie Bars by reducing some of the flour and adding oats to the crust and crumble mixture. The oats add such great texture.
The crust and oatmeal crumble topping are one and the same. Love it when that happens so there’s one less step and one less bowl to wash!
The blueberry oatmeal bars aren’t overly sweet and the blueberry flavor shines beautifully, which is why they’re great for breakfast, brunch, snacks, or a healthy dessert. They’re soft and tender, yet slightly chewy from the oats, and I’m a sucker for anything with a crumble topping.
Ingredients for Blueberry Oatmeal Bars
To make the oatmeal blueberry bars, you’ll need:
- Unsalted butter
- All-purpose flour
- Old-fashioned oats
- Granulated and brown sugar
- Salt
- Blueberries
- Lemon juice
- Cornstarch
How to Make Blueberry Bars with Oatmeal Topping
This blueberry crumb bars recipe has been a reader favorite for years, both because the bars are delicious and because the prep work is so simple!
- Make the crust / topping mixture: Melt the butter in a large bowl before adding in some flour, oats, two types of sugar, and salt. Stir all of that together. Note that the mixture should be dry and sandy at this stage.
- Set some of the mixture aside to be sprinkled on later as the oatmeal crumble topping, then transfer the rest to a greased 8×8-inch baking pan. Pack the mixture into the pan with your hands or a spatula (just make sure it’s packed down into an even layer and covers the entire pan).
- Make the blueberry filling: In the same bowl you made the topping in, add some blueberries, cornstarch, lemon juice, and sugar.
- Toss to combine, then spread the blueberry filling over the crust.
- Sprinkle the reserved crumble topping over the blueberry layer before popping the blueberry bars into the oven.
- Bake: The edges should be just set and the oatmeal crumble topping will be golden.
Blueberry Bars FAQs
I used frozen blueberries for these blueberry crumble bars, but I’m sure fresh would work as well. If you’re using fresh blueberries for these bars, I recommend reducing the bake time by 10 to 15 minutes (I haven’t made this recipe with fresh berries, so I can’t say for certain). When evaluating the doneness of your bars, it’s more important to decide based on how the bars look rather than how much time has passed.
Don’t use quick cook or instant oats because they’re finer than old-fashioned oats and behave like flour. Instant oats will make mixture too dry.
Yes, of course! I’ve also made Strawberry Bars, Mango Bars, and Cranberry Bars using this same base recipe.
Yes! I made this recipe for blueberry oat bars in a 8×8-inch pan, but you should be fine to double the recipe and bake the blueberry crumble bars in a 9×13-inch dish.
Absolutely! These bars freeze incredibly well and will last up to six months if sealed tightly in a freezer bag or freezer-safe container. So go ahead and make a pan or two of these bars when blueberries are in season and thaw them out when you have guests coming over!
I haven’t ever tried any of those flour alternatives, so can’t say for sure. My hunch is no, you can’t use anything besides all-purpose flour, because the flour serves the purpose of making both the crust and crumble. I would stick with all-purpose flour OR use a gluten-free all-purpose flour baking substitute if that’s the issue for you.
Tips for the Best Blueberry Bars
Cooling time: I should note that you can’t eat these bars straight out of the oven. These blueberry bars need time to cool and set (around 30 minutes or so). If you try to cut into the bars right away, they’ll fall apart in your hands and will likely scald the roof of your mouth.
Lemon blueberry bars: To make blueberry bars with a hint of lemon flavor in the filling, add the zest of a lemon to the filling. Don’t add extra lemon juice, as that would make the filling too runny.
Frozen berries: If using frozen berries, do not thaw them first. Add them to the filling straight from the freezer.
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Blueberry Bars with Oatmeal Crumble Topping
Ingredients
Crust and Crumble Topping
- ½ cup unsalted butter, melted
- 1 cup all-purpose flour
- ¾ cup old-fashioned whole-rolled oats, don’t use quick cook or instant, they’re finer and behave like flour and will make mixture too dry
- ½ cup granulated sugar
- ¼ cup light brown sugar, packed
- pinch salt, optional and to taste
Blueberry Layer
- 12 ounces 2 cups blueberries (fresh or frozen; I used frozen and didn’t thaw)
- ⅓ cup granulated sugar
- 2 tablespoons lemon juice
- 2 teaspoons cornstarch
Instructions
- Preheat oven to 350F. Line an 8-inch square pan with aluminum foil and spray with cooking spray; set aside. Lining the pan helps with cleanup and is recommended.
Make the Crust and Crumble Topping
- In a large, microwave-safe bowl melt the butter, about 1 minute on high power.
- Add the flour, oats, sugars, optional salt, and stir to combine. Mixture will be dry and sandy with some larger, well-formed crumble pieces.
- Set 1 heaping cup mixture aside to be sprinkled on later as crumble topping.
- Transfer remaining mixture to prepared pan, and using a spatula or your fingers, hard-pack the mixture to create an even, smooth, flat crust; set aside.
Make the Blueberry Layer
- In a large mixing bowl (same one used for crust and crumble is okay), add all ingredients and toss to combine. If sugar hasn’t dissolved fully that’s okay because it liquifies while baking.
- Evenly distribute blueberry mixture over the crust.
- Evenly sprinkle with the reserved heaping 1 cup crumble topping mixture. Before sprinkling, I squeeze the mixture in my palm to encourage bigger crumble pieces to form.
Bake the Bars
- Bake for about 55 minutes, or until edges are set and center has just set. Crumble topping should appear set and very pale golden. I used frozen berries without thawing and the pan was very cold going into the oven. If using fresh berries, baking time will be reduced, but I’m not sure by how much, I’d guess at least 10-15 minutes, possibly less. Bars may take longer than 55 minutes if blueberries are very juicy. Watch your bars, not the clock, when evaluating doneness.
- Place pan on a wire rack and allow bars to cool for at least 30 minutes before slicing and serving. If you try to slice bars before they’ve cooled completely, they’ll be extremely messy and could fall apart. Bars will keep airtight at room temperature for up to 1 week, in the fridge for up to 10 days, or in the freezer for up to 6 months.
Notes
- Recipe adapted from my Blueberry Pie Bars
Nutrition
Nutrition information is automatically calculated, so should only be used as an approximation.
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More Desserts Using Blueberries:
Blueberry Pie Bars — Super soft, easy bars with a creamy filling, streusel topping and abundance of juicy blueberries.
Blueberry Crisp — The sweet juicy blueberries contrasted with the crispy and crumbly oat-based topping is just perfect!
Crustless Blueberry Pie – A FAST, crustless, no-mixer dessert that’s perfect for summer entertaining, picnics, or potlucks!! Somewhere in between pie, cake, and blondies is what you get with this FABULOUS blueberry dessert recipe!
Lemon Blueberry Bundt Cake with Lemon Glaze — Almost more berries than cake in this soft, fluffy lemon blueberry bundt cake! The lemon glaze is plate-licking delish!!
Lightened Up Blueberry Lemon Pound Cake — The blueberry-lemon combo is always a win, and so is pound cake that won’t break your caloric piggybank. This Lemon Blueberry Pound Cake is a keeper!
Blueberry Muffin Cake — This fast and easy cake tastes like a big buttermilk pancake that ran into a blueberry muffin on the way to the oven.
Blueberry Zucchini Bread— This blueberry zucchini bread is a quick, no-mixer recipe that’s sweet, but not too sweet. Each bite is bursting with fresh blueberries!
Blueberry Cream Cheese Cake — A light and tender blueberry sponge cake stuffed with tangy-sweet cream cheese filling and bursting with juicy blueberries in every bite! An EASY, no-mixer cake recipe that’s sure to be a family FAVORITE!!
I think that it will taste deliciouse
Oh Em Geeeeeee!
Amazingly GOOD & easy!
You had me at melting the butter instead of having to cut it in.
Crust is do buttery & oaty & a perf CT platform for the filling.
Chilled bars get better & better 👍
I used fresh blueberries & plan to try sour cherries, peaches, plums. Seedless grapes?
Glad these are a hit with you and I agree, melted butter is just SO much easier than trying to cut butter in!
We love this recipe. It’s so easy and yummy. At least with the blueberries and oatmeal, it seem a little more healthy! Thanks,
Glad this is a favorite for you and I agree on the healthier side!
Hi Averie! I love making these bars and they’re always a hit whenever I do. Just a question though: Is there a way to make sure the filling isn’t too runny/the bars don’t fall apart? I’m never able to get the nice, solid bars you’re able to in your pictures. The only time I sort of do is when they’re in the fridge but once I take them out they start to fall apart easily. The only substitution I’ve ever made was using bottled lemon juice instead of fresh but they come out the same no matter what I do. Should I try adding more cornstarch to the blueberry layer?
Thanks for the 5 star review and glad you love these bars! To make them more solid, I would increase the amount of flour by a couple tablespoons and see if that helps. Corn starch will not do the trick I don’t think. Also use King Arthur brand flour. So much better for baking than other brands and I find it really helps add structure to my baked goods.
This has been a go to now for a couple years. Each time I make it i am reminded how easy as well as delicious it is! Always get compliments from guests.
Thanks for the 5 star review and glad you love this recipe and that it’s a go-to!
I love how I already had all the ingredients and so I decided to make it on a whim today. I used gluten free flour instead since my hubby can’t have gluten. He totally loved it and said it was soo good. Thanks for the easy recipe.
Thanks for the 5 star rating and glad it came out great for you! Good to know GF flour was a success, too!
I created a monster. He ate the whole pan in 2 days and wanted more but wanted to double it. 😳
A family favorite. Made these many times with a little more healthier version by using only whole wheat flour, and only a scant 1/2 cup of coconut palm sugar ( instead of white or brown sugar) in crumble mixture as well as a heaping 1/2 tsp of cinnamon.
I also sprinkled just a little coconut palm sugar ( no white sugar) over blueberries with the lemon juice and cornstarch.
Used frozen Oxford wild blueberries ( these are sweet on their own) and baked for about 45 – 50 minutes. These are excellent squares. Everyone really enjoys them. Thank you so much for this recipe.
Thanks for letting me know these are an absolute fave of yours and that you have even healthified them a bit!
going to try this for Christmas with ice cream. Will try to switch it up a notch. Mixed berries, coconut, cinnamon ….will try it and let you know how it goes!
Great, enjoy!
Will this work with oil instead of butter?
No, you need butter to actually make the crumbles, oil is oil and they won’t form.
Thanks for sharing the recipe. Just like eating a pie but portable!!! It does a bit too sweet for breakfast bar haha… but perfect for a treat or dessert, especially during my break on hiking trip. Seriously easy and fool proof, thumbs up.
Thanks for trying the recipe and I’m glad you enjoyed it!
I love this recipe and have made it several times. I’ve served them for dessert with a little scoop of ice cream or coconut gelato or by themselves. I’ve now started cutting the white sugar to half the amount called for in both the crust and filling and they are still sweet enough for us. Thank you for posting this!
Thanks for trying the recipe and I’m glad it comes out great for you with half the white sugar!
I love this recipe, as does my family. Made with blueberry, raspberry, cherry & peach. All were good. I added a little chopped crystallized ginger to the peach. Fab! Also parchment paper sprayed with spray
Thanks for trying the recipe and I’m glad it came out great for you! Glad you’ve experimented with other fruits, too!
I made these yesterday with my typical substitutions of whole wheat pastry flour, evaporated cane juice, and sucanat, and I omitted the lemon juice (personal preference). I also lined the pan with parchment instead of foil. I was a little worried that after removing 1 cup to reserve for the topping there wasn’t enough of the crumble mixture to make a nice sturdy bottom so I reduced the topping amount a little and added it to the crust layer. I used fresh berries and baked for 45 minutes. The bars came out awesome and husband loved them! Thank you for a great recipe.
Glad that your subs worked well and that you and your husband loved the bars!
I made it exactly as the recipe except I used parchment paper. It came out PERFECT!!!!! Thank you so much for the recipe. I plan to try with local strawberries next!
Thanks for trying the recipe and I’m glad it came out great for you! I have a raspberry version here as well https://www.averiecooks.com/raspberry-oatmeal-crumble-bars/
I wish I had tried parchment paper instead…the foil was a DISASTER! I also used fresh blueberries and cooked longer; but, what an ordeal getting them off the foil…Never again!!!
I use Reynolds nonstick foil that I spray with cooking spray for nearly 100% of my recipes that I bake in a pan and I have more than 3000 recipes on my site and I’ve never had any problems with anything ever sticking to foil but I’m sorry that you did. If you filled it using parchment paper or nothing would be better in the future then go for it. Thanks for trying the recipe.
So good, thankyou
Thanks for trying the recipe and I’m glad it came out great for you!
I made these last week and my husband LOVED them! He took one everyday for his breakfast. I used half fresh and half frozen blueberries and it baked perfectly. The only thing I will do differently next time is not use the foil. Even though I greased it, it was coming off onto the bottom of the bars. Next time I’ll just grease the pan. I would rather have a little more cleanup than foil getting in my way.
Great recipe!
I use Reynolds Heavy Duty *nonstick* foil, it’s a little more expensive but it never sticks. Just as an aside and a tip.
Glad you loved the bars and they were a big hit!