Buttery oatmeal crumbles and sweet, juicy berries make these Mixed Berry Crumble Bars impossible to resist. These bars use the same mixture for the oatmeal base and crumble topping, then the middle is a juicy layer of strawberries, blueberries, raspberries & blackberries that tastes just like summer.
These mixed berry crumble bars have a soft, brown sugar, oatmeal base; juicy berry centers; and delicious cinnamon, crumble topping. They taste like your favorite fruit crumble – only they’re easier to transport and have a higher ratio of oatmeal to berries. (Talk about win-win). Plus, they can be made with fresh or frozen berries.
I’ve actually shared quite a few crumble bars on Just So Tasty before. But I don’t think you can have enough easy fruit desserts. And since different kinds of berries have different levels of juice – you actually need to adapt the recipes depending on the type of fruit you’re using. Otherwise, you can end up with bars that are too soggy, which we definitely don’t want.
Berry Crumble Bars
For this recipe, I decided to make an extra large batch in a 9×13 inch pan. Feel free to half the recipe and make it in an 8×8 inch pan if you prefer (the bake time will be about the same.
For the Oatmeal Base & Crumble Topping
For the base & topping you only need a few simple ingredients:
- white sugar
- brown sugar
- melted butter – I actually prefer salted for this recipe
- 1 large egg
First, you’ll whisk together the sugars, flour, cinnamon & oatmeal. Then stir in the melted butter and egg. The mixture should look like wet sand, and if all the flour isn’t totally incorporated that’s ok. You should be able to squeeze it in your palm it should hold together.
You’ll reserve about 1 ½ cups of crumble for the topping, then press the rest of the crumble into the bottom of the lined pan.
For the Juicy Berry Middle
The berry layer is made by tossing together your berries, a little lemon juice, sugar and cornstarch. You can use fresh or frozen berries, and really any combo of chopped strawberries, raspberries, blueberries and blackberries. The lemon juice helps to brighten the flavor of the bars (don’t worry – you don’t actually taste lemon), and the cornstarch thickens the mixture.
A few notes about the berry filling:
- If using frozen berries, don’t thaw them first.
- Make sure to chop your strawberries and any large blackberries. I keep the raspberries and blueberries whole.
- If using frozen berries, only use 1 tablespoon of lemon juice instead of 2.
- Don’t forget the cornstarch – otherwise, the berry layer can be too juicy.
- If there’s a lot of juice in the bottom of your bowl after tossing the filling ingredients together, don’t add all of the juice to your bars. Otherwise, they can get too watery.
Then spoon the berry mixture over top of the oatmeal base, and crumble the remaining crumble on top. Squeezing it between your hands as you go. The bars will bake for about 50 minutes, and you’ll know they’re done when the top is golden brown and you can see the fruit below bubbling through.
When making these bars – it’s extremely important that they’re completely cooled before cutting into them. Otherwise, they can be a big jammy mess. Make sure you allow for at least 4 hours to cool the bars before you slice into them and enjoy.
These mixed berry crumble bars taste delicious with a scoop of ice cream for dessert, or cold from the fridge. I’ll happily eat them for dessert or breakfast, and they make for such an easy, simple dessert recipe.
For more fruit crumble recipes, try these other favorites:
Mixed Berry Crumble Bars
Oatmeal Base & Topping
- 2 ½ cups all-purpose flour
- 1 teaspoon cinnamon
- 1 ½ cups large flake or old-fashioned oats*
- 1 cup white sugar
- ½ cup brown sugar
- 1 cup butter melted
- 1 large egg
- 4 ½ cups mixed berries**
- ½ cup white sugar
- 2 tablespoons lemon juice*** freshly squeezed
- 3 tablespoons cornstarch
- Preheat the oven to 350F degrees.
- Line a 9x13 inch pan with parchment paper leaving an overhang around all the edges, or line with aluminum foil & lightly grease.
- In a large bowl stir together the flour, cinnamon, oats, & sugars
- Stir in the melted butter and egg. It should look like wet sand.
- Reserve about 1 ½ cups of the mixture for the topping. Then press the rest (about ⅔ of the batter) into the bottom of the prepared pan.
- In a large bowl toss together the berries, sugar, lemon juice & cornstarch so that the berries are evenly covered.
- Spoon the berry mixture over top of the base.
- Crumble the remaining oatmeal mixture over top squeezing it in your palms so that large crumbles form.
- Bake in the preheated oven for 45-50 minutes, or until the top is golden brown and you can see the berry mixture bubbling through.
- Cool the pan on a wire rack at room temperature for 30 minutes, then move to the fridge to continue cooling (this can take up to 4 hours). before
- Once the pan is completely cooled, slice into bars. Store in an airtight container in the fridge for up to 4 days.