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    Home » Recipes » Bars Brownies & Slices

    Lemon & Blueberry Crumble Bars

    Published: Jun 15, 2022 by Lucy · This post may contain affiliate links · 31 Comments

    Jump to Recipe
    A piece of slice with a blueberry and creamy lemon filling, and a crunchy golden crumble topping.

    Sweet and delicious Blueberry Crumble Bars with a creamy lemon filling. Perfect for morning tea or a late night dessert treat, these crumble bars take just 20 minutes to prepare and taste amazing served either warm or cool.

    Don't be fooled... they may look fancy, but they're SO simple to make.

    Pieces of blueberry crumble bars on a white cake stand.

    These Lemon & Blueberry Crumble Bars are the answer when you have to choose between baking a dessert or a slice... and the choice is impossible!?

    This recpe ticks ALL the boxes as both a decadent dessert and a tasty morning tea slice.

    Just like my classic apple crumble slice, white chocolate and raspberry cheesecake slice and my famous brownies, these blueberry crumble bars are the perfect option at anytime of the day (or night!).

    You can serve them cool on their own, or warmed up and drizzled with your favourite custard, cream or ice-cream as a simply scrumptious dessert!

    Blueberry crumble slice with lemon filling.

    Why You're Going To Love This Recipe

    Once you try lemon blueberry crumble bars, you're going to have a new family favourite recipe... I promise!

    • PACKED full of flavour - this slice has allllll the flavour you could possibly dream of! Sweet, crunchy streusel topping and base, combined with bursts of blueberries and a HEAVENLY creamy lemon filling.
    • Fresh, zesty, light and creamy - I like to use a combination of lemon zest, lemon juice and lemon extract to really bump up the lemon flavour! But you can omit the lemon extract if you like (or if you don't have any at home). The lemon zest and lemon extract give the slice the strongest lemon flavour, while the lemon juice thickens the sweetened condensed milk filling.
    • Looks fancy but is SO easy to make - while this layered slice may look impressive, it's actually incredibly easy to make! The crumble base and topping is made using the same mixture and the lemon filling is made using just one bowl and a whisk. SO simple!
    • Can be served warm or cold - don't get me wrong, this is delicious served cold... but my favourite option is to heat it up a little and add a scoop of ice-cream or a drizzle of cream as a simply indulgent dessert.
    • Freezer-friendly - pop any leftovers in the freezer for up to 3 months.
    • Thermomix and conventional methods - these blueberry and lemon crumble bars can be made conventionally using a spoon and bowl, or in a Thermomix. I've included both methods in the recipe card at the bottom of the post.
    A close up of a blueberry crumble bar with more pieces in the background.

    What You Need

    Lemon and Blueberry Crumble Bars are made using a handful of basic ingredients - many of which you will already have at home!

    Note: please scroll to the recipe card at the bottom of the post for ingredient quantities and the full detailed method.

    All the ingredients set out on a marble bench top.

    For The Crumble

    • Plain flour - also known as all-purpose flour.
    • Rolled oats - also known as old fashioned oats. It's best to use rolled oats rather than quick oats as they give the crumble a much nicer texture and crunch!
    • Salt - a pinch of salt in the crumble perfectly balances the sweetness and creaminess of the lemon filling.
    • Bi-carbonate soda - also known as baking soda.
    • Raw sugar - this crystallised sugar gives the crumble it's epic CRUNCH!
    • Brown sugar - while the raw sugar gives the crunch, the brown sugar adds a tasty chewiness and caramel flavour to the crumble.
    • Butter - you can use either salted or unsalted butter. If using salted butter, omit the extra pinch of salt.
    • Vanilla extract - you can use either vanilla extract or vanilla essence for this recipe.

    For The Filling

    • Sweetened condensed milk - use full fat (not skim) sweetened condensed milk as it sets firmer.
    • Lemon zest - this gives the filling it's lemony flavour - add extra lemon zest if you're a real lemon lover.
    • Lemon juice - the lemon juice reacts with the dairy in the sweetened condensed milk, causing it to thicken the mixture.
    • Egg yolks - have your egg yolks at room temperature.
    • Lemon extract - this is optional but really does give the filling an extra lemony kick! Personally, I love it, but you might find that the lemon zest and lemon juice are enough all on their own for you.
    • Blueberries - you can use either fresh or frozen blueberries in this recipe.

    Equipment Required

    You may think this decadent slice looks a little tricky, but it's actually incredibly easy to make! ... and no fancy equipment required.

    • Microwave, Thermomix or stove top - to melt the butter.
    • Oven - I specify fan-forced oven temperatures in my recipes, so if you have a conventional oven, increase the temperature by between 10 and 20 degrees Celsius.

    Step By Step Instructions

    The crumble mixture is the same mix as the base, and the blueberries and creamy lemon filling are layered between the base and crumble - so....simple....

    Note: please scroll to the recipe card at the bottom of the post for ingredient quantities and the full detailed method.

    Step 1 - Prepare The Crumble

    Place the plain flour, rolled oats, salt, bi-carbonate of soda, raw sugar and brown sugar into a large bowl and mix together to combine.

    Flour and sugars added to a glass bowl.

    Pour over the melted butter and vanilla extract.

    Melted butter being poured into dry oat mixture.

    Stir until all of the dry ingredients have been coated in the butter and the mixture is crumbly.

    Crumble mixture in a glass bowl.

    Press just over half of the crumble mixture into the base of a lined slice tin (I use an 18cm x 28cm rectangular tin).

    Bake for 15 minutes until lightly golden.

    An oat slice base pressed in to a paper lined tray.

    Step 2 - Add The Blueberries

    Sprinkle the fresh or frozen blueberries over the cooked base.

    Blueberries sprinkled over an oat slice base.

    Step 3 - Make The Lemon Filling

    Place the sweetened condensed milk, lemon zest, lemon juice, egg yolks and lemon extract (if using) into a large bowl.

    Eggs, condensed milk and lemon zest in a glass bowl.

    Whisk together until smooth and the filling has thickened slightly.

    A creamy lemon mixture in a bowl.

    Pour the lemon filling over the blueberries and smooth out with the back of a spoon.

    Creamy lemon filling with blueberries in a slice tin.

    Step 4 - Sprinkle Over The Remaining Crumble

    Use your fingers to sprinkle the remaining crumble over the filling.

    Note: it's fine if there's some small sections of filling not covered in crumble.

    Bake for 23-26 minutes or until golden and crunchy on top.

    Crumble mixture sprinkled over base in a rectangular slice tin.

    Serving Suggestions

    The wonderful thing about this lemon and blueberry crumble slice (apart from the fact that it's absolutely delicious) is that it can be served warm or cool.

    If serving warm, try serving with:

    • a scoop of vanilla ice-cream
    • homemade vanilla custard
    • a drizzle of berry coulis
    • a spoonful of thickened or whipped cream.

    The perfect option for morning tea, afternoon tea or dessert!

    A piece of crumble slice on a white and gold plate with a gold fork resting on the plate next to it.

    FAQs

    Making blueberry crumble bars with a creamy lemon filling is SO easy!

    Here's some of my readers most common questions answered...

    Can I use coconut condensed milk instead of sweetened condensed milk?

    No. The lemon juice reacts with the dairy in the sweetened condensed milk which is what causes the filling to thicken. As coconut condensed milk contains no dairy, it will not thicken.

    Can I use either fresh or frozen blueberries?

    Yes, absolutely! Frozen blueberries tend to be more juicy when baked, but both are quite delicious.

    Is it important to use lemon extract?

    As this recipe uses lemon juice and lemon zest, you can omit the lemon extract if you prefer. However, it does give the slice an extra lemony boost!

    A gold fork with a creamy lemon and blueberry crumble bars on it.

    Expert Tips

    Follow my tips for baking the perfect lemon and blueberry crumble slice every time!

    • All ovens are different - the slice is ready when the crumble is golden. I specify degrees celsius (fan-forced) for my recipes. If you're using a conventional oven, increase the temperature by 10-20 degrees celsius.
    • If you find that your crumble is over-browning, simply add a sheet of foil loosely over the top and continue baking.
    • You can substitute the blueberries for strawberries, raspberries or blackberries if you prefer (or a combination of different berries!)
    • This crumble slice is delicious served cool or warmed up with a scoop of ice-cream, custard, cream and/or berry coulis.
    • Cut the slice using a sharp serrated knife.
    • Store the slice in an airtight container in the fridge for up to one week.
    • Freeze the slice in an airtight container for up to 3 months. Allow to defrost in the fridge before consuming.

    More Blueberry Inspired Recipes

    Blueberries are perfect for baking - with their sweet little bursts of flavour, they make the perfect addition to any slice or dessert.

    • a slice of cheesecake with a bite missing
      No Bake Blueberry Cheesecake
    • A spoonful of oat baked crumble with blueberries and apple.
      Apple and Blueberry Crumble
    • A half-eaten sweet white muffin with blueberries mixed throughout.
      Easy Blueberry Muffins | Cafe-Style
    • Blueberry and lemon cookies on a white cake stand.
      Lemon & Blueberry Thumbprint Cookies

    WANT EVEN MORE DELICIOUS RECIPES? Subscribe to my newsletter or follow along on Facebook or Instagram. And if you love baking, then please come and join my Facebook cooking club group or subscribe to my YouTube channel.

    Blueberry crumble slice with lemon filling.

    Lemon & Blueberry Crumble Bars

    The most delicious Lemon & Blueberry Crumble Bars! Creamy, tangy and oh-so sweet... the perfect dessert or afternoon treat!
    5 from 29 votes
    Print Pin Rate
    Course: Dessert, sweets
    Cuisine: Slices
    Prep Time: 20 minutes minutes
    Cook Time: 38 minutes minutes
    Total Time: 58 minutes minutes
    Servings: 16 serves
    Calories: 368kcal
    Author: Lucy - Bake Play Smile

    Ingredients

    • 155 g (1¼ cups) plain flour
    • 110 g (1¼ cups) rolled oats
    • ½ teaspoon salt
    • ½ teaspoon bi-carbonate of soda
    • 100 g (½ cup) raw sugar
    • 80 g (½ cup) brown sugar packed
    • 170 g (¾ cup) butter melted
    • 1 teaspoon vanilla extract
    • 200 g (1 cup) frozen blueberries or fresh
    • 395 g (1 tin) sweetened condensed milk
    • 1 tablespoon lemon zest finely grated, approximately 1 lemon
    • 85 g (⅓ cup) lemon juice
    • 2 large egg yolks
    • ½ teaspoon lemon extract optional

    Instructions

    Conventional Method

    • Preheat oven to 160 degrees celsius (fan-forced.
    • Grease and line a 18cm x 28cm slice tray with baking paper, allowing the edges to overhang.
    • In a large bowl, whisk together the plain flour, rolled oats, salt and bi-carbonate of soda.
    • Stir in the raw sugar and brown sugar and mix until smooth.
    • Stir vanilla extract into melted butter and pour mixture over dry ingredients.
    • Stir mixture until well combined.
    • Press just over half of the crumble mixture into the base of the prepared tin and use the back of a spoon to smooth the mixture into an even layer. Bake in the preheated oven for 15 minutes, until golden.
    • Remove from oven and put aside (leave the oven turned on).
    • Sprinkle the blueberries over the cooked crumble base. 
    • In a bowl, whisk together sweetened condensed milk, lemon zest, lemon juice, egg yolks and lemon extract (optional) until smooth and slightly thickened.
    • Pour the lemon mixture over the blueberries and spread into an even layer.
    • Sprinkle the remaining crumble mixture over the top of the lemon filling and blueberries.
    • Bake in oven for 23 - 26 minutes or until lightly golden.
    • Remove from oven and allow to cool.
    • Cover and refrigerate for at least 2 hours (preferably overnight) then take it out and cut into squares. Store in airtight container in the refrigerator for up to 1 week.

    Thermomix Method

    • Preheat oven to 160 degrees celsius (fan-forced).
      Grease and line an 18cm x 28cm slice tray with baking paper, allowing the edges to overhang.
    • Melt the butter and vanilla extract in the Thermomix bowl for 3 minutes, Speed 2, 80 degrees.
    • Add the plain flour, rolled oats, salt, bi-carbonate of soda, brown sugar and raw sugar. Mix for 20 seconds on Reverse, Speed 2. Scrape down the sides. Mix for a further 20 seconds on Reverse, Speed 2.
    • Press just over half of the crumble mixture into the base of the prepared tin and use the back of a spoon to smooth the mixture into an even layer. Bake in the preheated oven for 15 minutes, until golden.
    • Remove from oven and put aside (leave the oven turned on.
    • Place the zest of 1 lemon into the Thermomix bowl. Grate for 20 seconds, Speed 6. Scrape the sides of the bowl. Repeat until you have a very finely grated zest.
    • Add the sweetened condensed milk, lemon juice, egg yolks and lemon extract (optional) and mix for 30 seconds, Speed 4. Scrape the sides of the bowl and mix for a further 30 seconds, Speed 4.
    • Sprinkle the blueberries over the cooked crumble base. Pour lemon mixture over the blueberries and spread into an even layer.
    • Sprinkle the remaining crumble mixture over the top of the lemon and blueberries.
    • Bake in oven for 23 - 26 minutes or until lightly golden. Remove from oven and allow to cool.
    • Cover and refrigerate for at least 2 hours (preferably overnight) then take it out and cut into squares. Store in airtight container in the refrigerator for up to 1 week.

    Notes

    RECIPE NOTES & TIPS:
    • All ovens are different - the slice is ready when the crumble is golden. I specify degrees celsius (fan-forced) for my recipes. If you're using a conventional oven, increase the temperature by 10-20 degrees celsius.
    • If you find that your crumble is over-browning, simply add a sheet of foil loosely over the top and continue baking.
    • The lemon extract gives the slice an extra lemony flavour, but you can omit it if you prefer. 
    • You can substitute the blueberries for strawberries, raspberries or blackberries if you prefer (or a combination of different berries!)
    • This crumble slice is delicious served cool or warmed up with a scoop of ice-cream, custard, cream and/or berry coulis.
    • Cut the slice using a sharp serrated knife.
    • Store the slice in an airtight container in the fridge for up to one week.
    • Freeze the slice in an airtight container for up to 3 months. Allow to defrost in the fridge before consuming.

    Nutrition

    Calories: 368kcal | Carbohydrates: 57g | Protein: 7g | Fat: 13g | Saturated Fat: 8g | Cholesterol: 57mg | Sodium: 150mg | Potassium: 206mg | Fiber: 3g | Sugar: 29g | Vitamin A: 380IU | Vitamin C: 4mg | Calcium: 95mg | Iron: 1.9mg
    Did you try this recipe?Mention @BakePlaySmileBlog or tag #BakePlaySmile!

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    Comments

    1. Theresa says

      June 19, 2020 at 1:47 pm

      hi just wandering, any ideas to getting the base even so not too thick ?
      kind regards .

      Reply
      • Lucy says

        June 20, 2020 at 8:36 am

        Hi Theresa, I'm not sure I understand what you mean sorry? In terms of getting the base even, I like to use the back of a spoon to press it down firmly. The base does need to be a little thick to be able to hold the filling and topping. Hope that helps?

        Reply
    2. Vanessa says

      September 26, 2019 at 10:09 pm

      I made this slice for the first time and it was definitely a favourite for everyone! Such a great recipe using ingredients I already had in the kitchen. I used fresh blueberries and it worked perfectly, will definitely be making it again. Thanks for a lovely recipe!

      Reply
      • Lucy says

        September 27, 2019 at 5:51 am

        Yay! That's fantastic!!! xx

        Reply
    3. Teresa Smith says

      August 26, 2019 at 10:38 am

      5 stars
      Wow delicious was a hit with every family member so I’m about to cook it again.

      Reply
      • Lucy says

        August 27, 2019 at 9:16 am

        That's so fantastic to hear! Thank you!!!

        Reply
    4. Belinda says

      August 24, 2018 at 7:03 pm

      5 stars
      I made this for morning tea at work today and it was a hit. It went so quickly. I could hear people saying how lovely it was. Will definitely be making this again. Thanks!

      Reply
      • Lucy Mathieson says

        August 24, 2018 at 7:10 pm

        Yay!!! I'm so happy you enjoyed it!

        Reply
    5. Natalie says

      June 07, 2018 at 3:35 pm

      H i Lucy, I made this last night and it was a hit at work. While the slice was delicious I found that that after refrigerating overnight, the slice was quite "sticky". It kind of fell apart and was gooey which made it difficult to pick up an individual slice. By the end of the day the sugars had made the bottom of the slice sticky. Do you have any idea as to why this would have happened?

      Thanks - love the recipe though and will make again.

      Reply
      • Lucy Mathieson says

        June 07, 2018 at 5:05 pm

        Hi Natalie, Yes you're absolutely right the bottom can go a bit sticky! It's generally because of the liquid from the blueberries. Fresh blueberries tend to not go as sticky but still a little bit!

        Reply
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    I’m Lucy! A mum, a wife, a food blogger and a lover of all things to do with food! I love creating delicious, no-fuss Thermomix and conventional recipes the whole family will love. Classic baking favourites, lunch box snacks, quick and easy family dinners and more!

    More about me →

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