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!!
The blueberry crumble bars are great. I used fresh berries and baked for 40 min and doubled the streusel. I also added vanilla and almond extract to the filling.
Thanks for trying the recipe and I’m glad it came out great for you! I love both almond and vanilla extracts!
I cut the sugar by 2 and put more of flour. It’s very good and perfect! ;-)
Thanks for trying the recipe and I’m glad it came out great for you with the changes you made.
Hello Averie! We don’t have fresh or frozen blueberries from where I live. Is it okay to use those in can? The only blueberries we have here is canned blueberries.
I don’t have any experience working with canned blueberries so can’t say for sure. If they are already sweetened like blueberry pie filling then I would omit the sugar.
I doubled the receipt using a 9 x 13 dish. 1/2 demerara brown sugar and 1/2 blue agave for the crust along with the packed brown sugar; 1/2 butter and 1/2 coconut oil. The blueberries were out of the frig, not frozen. Checked at 40 minutes and took out at 45. They set up fairly well except around the edges. May be from the agave or may have needed another 5 minutes. I used parchment paper with a little coconut oil on it. Delicious!!! Half in tupperware and half into the freezer :-)
Thanks for trying the recipe and I’m glad it came out great for you even with all the tweaks!
Great recipe! And they looked just like the picture!! Will definitely use this recipe over and over. Highly recommend.
Thanks for trying the recipe and I’m glad it came out great for you!
Loved this recipe! It has become a summer staple with fresh blueberries! I have also tried your other bar recipe (“Berry Crumble Bars”), but I think the oats in this recipe give it a nice texture! I reduced the sugar in the berries to 1/4 cup, since the blueberries I had were on the sweeter side and the recipe was perfect! Thanks for sharing the recipe!
Thanks for trying the recipe and I’m glad it came out great for you! I agree, the oats in this one make it especially good :)
My husband RAVED about these bars for weeks, it was almost concerning. Super simple recipe that is super delicious. We inherited 14 huge blueberry bushes with our new house, so this recipe will be with us for a long time. Wouldn’t change a thing! Thank you for sharing it.
Thanks for trying the recipe and I’m glad it came out great for you!
I am super jealous of your blueberry bushes! I just moved into a new house in San Diego (where anything grows) and I was seriously considering planting blueberry bushes but was very afraid they’d just be candy for the birds and squirrels! Sounds like it’s possible to have a homegrown crop based on your story!
Thank you for a great recipe!
I’m too lazy to wake up early in the morning – to bake something more elaborate for breakfast; and the size of the bake fit my toaster oven – no need to use the big oven – :)
Although your blueberry bars were easy and fast to make, they are really good. I had to change filling – I had 1 cup of fresh blueberries only. I took 1 diced apple – so together I had 2 cups of mixed fruit/berries. I cooked this apple briefly in sugar and lemon juice – to get rid of extra moisture. After some liquid evaporated, I mixed in starch and blueberries.
The crust/topping were made exactly as in your recipe and it is to die for – :) Will definitely make it again, whenever I have leftover berries.
Thanks for trying the recipe and I’m glad it came out great for you! Way to improvise with the apple + blueberries!
The recipe is great! I tripled it. I am pleased with the result except that the tin foil baked onto my pan! It only peels off in little shards. I’m not sure what I did wrong, but I think I would try parchment next time or else really grease the pan.
Different brands of foil vary in thickness and durability. I use very heavy duty foil. I like foil in this recipe because the juice of the blueberries, with the sugar, and the metal pan…things can get really sticky/stuck and I find foil easier but do what you think will work best. Glad you loved and tripled the recipe!
The step about cooking spray is no joke. Absolutely use foil and coat the sides of the lined pan like your life depends on it!
And don’t skimp on the foil. Make sure that bad boy is COVERED. It gets hot and bubbly before it becomes a seriously sticky awesomeness. It took me no less than 20 minutes to cut and remove 4 pans of bars (9 squares each).
Learn from my mistakes. Use lots of foil and cooking spray.
There is something about fruit + sugar + heat that produces the most seriously sticky concoction, I know! Thanks for trying the recipe.
Made BLUEBERRY OATMEAL CRUMBLE BARS tonight and I can tell you they won’t last long! I’m not a fan of white flour so I did use 1/2 white and 1/2 whole wheat. My husband loved them. May even try a more whole wheat and less white flour the next time. Also I used frozen blueberries. Thank you for sharing :)
Thanks for trying the recipe and I’m glad it came out great for you! Glad that you were able to get away with some w.w. flour, too!
Your blueberry bar recipe is absolutely delicious, i tweaked a few ingredients and OMG it will be one that I repeat over and over. Thanks, I will feature it in my blog sugarsaltspice.com I will give you credit for this. Love your blog.
Thanks for trying the recipe and I’m glad it came out great for you! Glad it will be on repeat!
I made these using strawberries. My husband loved them, he said they were sweet. I meant to reduce the amount of sugar due to the sweetness of the strawberries, but my mother called just as I started, so I ended up just
following the recipe.
My husband started suggesting other fruits to use, bananas, apples, so I will have to do some experimenting. Thanks for a great recipe.
I’ve made them with raspberries! https://www.averiecooks.com/2016/01/raspberry-oatmeal-crumble-bars.html
I think I need to make them with strawberries this summer! Glad you loved them!
This is a perfect recipe! I didn’t change any measurements and they came out perfect. I used my gluten free flour blend one for one as you would regular flour. I can’t wait to try with cherries or raspberries. Thank you for a great recipe! This will be on rotation in our house.
Thanks for trying the recipe and I’m glad it came out great for you! Even with GF flour!
Looks sooO good! can’t wait to try them!
Hi, I’m excited to try this recipe! I’m on a chia seed kick and like to try to find ways to add them to recipes to give it a healthy boost and because they have a bland flavor they shouldn’t alter the taste here. I’m still new to using chia seeds so my question is if you have experience with them, or if anyone has suggestions, which step here they should be added? Because they can become gel-like when mixed with liquid, I was thinking of adding them to the crust/crumb topping, but I didn’t know if the melted butter would doing something weird. Thoughts? Haha I know this is such an odd question, but a girl’s got to look for ways to be healthy when eating something that sounds so delectable! Thanks!
This wouldn’t be a recipe I’d add chia seeds to. There are too many things that can go wrong from the crust not setting, the crumble turning gooey on account of the chia seeds, the blueberry consistency becoming off from them – I personally wouldn’t add them here.