Blueberry Oatmeal Crumble Bars

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Blueberry Bars with Oatmeal Crumble Topping — 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!

four blueberry bars with oatmeal crumble topping on white plate

Easy Blueberry Crumble Bars Recipe

I was going to call these blueberry breakfast bars. Or blueberry snack bars. But anytime you feel like eating juicy blueberries with buttery oat crumbles is the kind of bar they are.

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! 

I also eliminated the Greek yogurt, sugar, and egg from the filling and kept the focus on the blueberries.

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.

My daughter said they’re one of the best ‘desserts’ I’ve made in a long time. I made these blueberry bars on a Sunday and had breakfast ready to grab-and-go for her for the week.

One less thing to worry about on busy weekday mornings! Loved that.

close up of blueberry bar with oatmeal crumble topping

Ingredients for Blueberry Bars

To make the blueberry oatmeal bars, you’ll need: 

  • Unsalted butter
  • All-purpose flour
  • Old-fashioned oats
  • Granulated and brown sugar
  • Salt
  • Blueberries
  • Lemon juice
  • Cornstarch 

Should I Use Fresh or Frozen Blueberries? 

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. 

Can I Use Instant Oats? 

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. 

Can I Use Another Type of Berry? 

Yes, of course! I’ve also made Strawberry Bars and Cranberry Bars using this same base recipe. 

Blueberry Oatmeal Crumble Bars - Fast, easy, no-mixer bars great for breakfast, snacks, or a healthy dessert! BIG crumbles and juicy berries are irresistible!!

How to Make Blueberry Bars

This blueberry crumble bars recipe has been a reader favorite for years, both because the bars are delicious and because the prep work is so simple! 

  1. Make the oatmeal crumble topping: 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. 
  2. 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). 
  3. Make the blueberry filling: In the same bowl you made the topping in, add some blueberries, cornstarch, lemon juice, and sugar.
  4. Toss to combine, then spread the blueberry filling over the crust. 
  5. Sprinkle the reserved crumble topping over the blueberry layer before popping the blueberry bars into the oven.
  6. Bake the bars until the edges are set and the oatmeal crumble topping is just turning golden. 

Blueberry Oatmeal Crumble Bars - Fast, easy, no-mixer bars great for breakfast, snacks, or a healthy dessert! BIG crumbles and juicy berries are irresistible!!

Can This Recipe Be Doubled? 

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. 

Can Blueberry Bars Be Frozen? 

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! 

Blueberry Bars with Oatmeal Crumble Topping — 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!

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. 

Blueberry Bars with Oatmeal Crumble Topping — 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!

Pin This Recipe

Yield: 8 servings

Blueberry Bars with Oatmeal Crumble Topping

Blueberry Bars with Oatmeal Crumble Topping

These Blueberry Bars with Oatmeal Crumble Topping 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! 

Prep Time 10 minutes
Cook Time 55 minutes
Cooling Time 30 minutes
Total Time 1 hour 35 minutes

Ingredients

Crust and Crumble Topping

  • 1/2 cup (1 stick) unsalted butter, melted
  • 1 cup all-purpose flour
  • 3/4 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)
  • 1/2 cup granulated sugar
  • 1/4 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)
  • 1/3 cup granulated sugar
  • 2 tablespoons lemon juice
  • 2 teaspoons cornstarch

Instructions

  1. 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

  1. In a large, microwave-safe bowl melt the butter, about 1 minute on high power.
  2. Add the flour, oats, sugars, optional salt, and stir to combine. Mixture will be dry and sandy with some larger, well-formed crumble pieces.
  3. Set 1 heaping cup mixture aside to be sprinkled on later as crumble topping.
  4. 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

  1. 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.
  2. Evenly distribute blueberry mixture over the crust.
  3. 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

  1. 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.
  2. 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

Nutrition Information:

Yield:

8

Serving Size:

1

Amount Per Serving: Calories: 414Total Fat: 12gSaturated Fat: 7gTrans Fat: 0gUnsaturated Fat: 4gCholesterol: 31mgSodium: 22mgCarbohydrates: 62gFiber: 2gSugar: 33gProtein: 4g

More Blueberry Dessert Recipes: 

ALL OF MY BLUEBERRY RECIPES!

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!

About the Author

Welcome to AverieCooks! Here you’ll find fast and easy recipes that taste amazing and are geared for real life. Nothing fussy or complicated, just awesome tasting dishes everyone loves!

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Please note: I have only made the recipe as written, and cannot give advice or predict what will happen if you change something. If you have a question regarding changing, altering, or making substitutions to the recipe, please check out the FAQ page for more info.

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Comments

  1. These bars are delicious but the large volume of ads in the post and recipe make it very cumbersome to use.

    Rating: 5
    1. I haven’t ever tried any of those so can’t say for sure although my hunch is no because the flour serves the purpose of making both the crust and crumble so I would stick with AP or use a GF-AF if that is the issue.

  2. I’d like to try these but can’t see any quantities for ingredients. Also, the popup ads on this site make it almost impossible to read.

  3. I made these bars last night for Sunday night dinner. They were a huge hit. As with All Recipes I use the recipe as a base and I personalize it .I doubled the recipe baked it in a 9 by 13 Pan buttered the Pan , used no foil or parchment paper. I added sliced almonds and cinnamon to the oat butter mixture.. For the blueberries I used frozen blueberries . I cooked it on a stove top , first, to activate the cornstarch lemon juice and to thicken up the juice that the blueberries will exude once they get heated up. I let cool down a little bit before I put it on the oat mixture. Baked 45 minutes and let it cool in pan for an hour before i served them. It was perfection. Thanks for the’ berry-good ‘ recipe. Risha

    Rating: 5
    1. I am glad these were a huge hit and that you were able to add almonds and cinnamon to the mixture and that frozen blueberries worked just fine for you!

  4. Hi I just made your Blueberry oatmeal crumble, and it tastes really good, the only issue is had was it sticking to the foil.
    I sprayed the foil with cooking spray like you suggested, I let it cool completely.
    I even put it in the refrigerator to chill, but it still stuck.
    So now instead of bars I have a crumble.

    What did I do wrong?

    Thanks

    1. Some foil is just that way. I always bake with this foil. When sprayed, it never ever sticks! https://amzn.to/3MvKZBj

      Also the foil is optional but for me I can’t cook without it because I don’t like doing extra dishes later :)

  5. Hi there I was wondering if I can use Splenda instead of sugar for the Blueberry oatmeal crumble bars.

    If I double the recipe will it take longer to cook?

    Thanks

    1. I am not sure, I have never baked with Splenda so can’t answer that.

      Possibly a bit longer, but if you bake it in a 9×13 pan, not much longer, maybe 5ish minutes or so. But cooking with Splenda could also effect baking time, so keep that in mind.

  6. The blueberry crumble bars were a major hit! I did use extra-thick oats and they came out great. I really appreciate your explanations of why to use particular ingredients (like don’t use the quick-cook oats because they act like flour in this recipe). Thank you so much for this delicious recipe:)

    Rating: 5
    1. Thanks for the 5 star review and glad these were a major hit! And I am glad you appreciate my explanations and tips, that is nice for me to know they are appreciated.

  7. Just made this tonight – delicious! And a great kid-friendly recipe for when the littles want to help mix :)

    Rating: 5
  8. for some reason, I tipped it upside down and the blueberries and toppings fell out so when I put it back in the toppings were mixed in with the blueberries. It still tasted good, would recommend but don’t tip it upside down. lol :).

    Rating: 5
    1. LOL! Thanks for the 5 star review and glad that this was still good even after a little mishap!

  9. When I made these, my crust crumble mixture was like dough, not crumbly. I even added an extra 1/2 cup of flour. Still turned out tasty, though. Is there something in the recipe that is misprinted? I’m a seasoned baker, and the only way I could see this getting crumbly is by cutting in the butter. I will definitely try it again!

    Rating: 4
    1. There are so many things but I would use King Arthur flour when baking, it’s got slightly more protein (gluten) and is insurance against these types of things because if you added 1/2 cup more flour, I am guessing your flour is a very soft flour, like Gold Medal or a no name brand. Also because of summer humidity, you will likely need to use more flour regardless for things but if you’re a seasoned baker then you know that.

      Also you want to use a light hand when mixing it together, sort of spoon, fluff, turn over, mix it with a fork not a spoon so you don’t have the temptation to ‘stir’. All of these things should help the mixture be more of a crumble for next time.

  10. Made with fresh blueberries, decreased the sugar in the blueberry filling for health reasons, and baked for 45 minutes. Came out perfect! Ppl need to remember to let cool completely

    Rating: 5
    1. Thanks for the 5 star review and glad that they came out great with less sugar and fresh berries, and yes, cooling completely is the only way with these!

  11. These bars were wonderful. I had fresh blueberries so I used 2 1/2 cups, which is what I had on hand. Turned out perfect bars. Thanks for the recipe.

    Rating: 5
  12. How do you tell when it’s “set”? My over takes an extra long time to bake everything, so it’s tricky for me to tell when things are done. I let it bake an extra 10 minutes, and it looked like yours did in the video. It turned out too mushy to be eaten as a bar though. It’s still delicious, but you have to eat it with a fork.

    Rating: 5
    1. Thanks for the 5 star review! Then it wasn’t set if it was too mushy to eat as a bar OR you just had really juicy berries. Either way, you probably could’ve baked a bit longer for a firmer texture but a fork works just fine too.

  13. This is an easy, delicious recipe.I made it once before with blueberries and today I used strawberries. Yum!

    Rating: 5
    1. Thanks for the 5 star review and glad it was easy and delicious and you are mixing up the fruit options!