Healthy Berry Oatmeal Crumble Bars (Easy Recipe!)

These Berry Oatmeal Crumble Bars are the perfect healthy-ish dessert, snack, or even breakfast treat! Featuring a buttery oat crumble base that doubles as the topping, and a sweet, slightly tart mixed berry filling, they are absolutely delicious and incredibly easy to make. I love baking with berries, especially during the spring and summer months (like right now in early May!), and these Berry Oatmeal Crumble Bars are a fantastic way to use up fresh or frozen berries. Made with whole wheat pastry flour and naturally sweetened elements, they’re a treat you can feel good about enjoying!

Why You’ll Love These Berry Oatmeal Crumble Bars

• Healthy & Wholesome: Made with oats, whole wheat pastry flour (or substitute), naturally sweetened filling, and packed with berries.
• Delicious Berry Filling: A simple mix of berries, maple syrup, lemon juice, and cornstarch creates a perfect jammy filling.
• Easy Crumble Method: The same oat mixture is used for both the crust and the crumble topping – so easy!
• Versatile: Great for breakfast, snacks, or dessert.
• Perfect Use for Berries: Ideal for using fresh seasonal berries or frozen berries year-round.

Ingredients for Berry Oatmeal Crumble Bars

Here’s what you’ll need to bake these delicious and healthy crumble bars. The full list with measurements is in the recipe card below.

Crust/Crumble Mixture

• Whole wheat pastry flour* (or sub all-purpose/regular whole wheat) (Flour)
• Oats (rolled oats recommended) (Grain)
• Baking powder (Leavening Agent)
• Cinnamon (Spice)
• Salt (Seasoning)
• Large egg (Binder)
• Brown sugar, loosely packed (Sweetener)
• Vanilla extract (Flavoring)
• Coconut oil, melted and cooled (Fat)

Berry Filling

• Berries (fresh or frozen mix – blueberries, raspberries, blackberries suggested) (Fruit)
• Cornstarch (Thickener)
• Freshly squeezed lemon juice (Acid)
• Pure maple syrup (Sweetener)

(Note refers to original recipe recommendation on flour type) (Note: the full ingredients list, including measurements, is provided in the recipe card below.)

Variations

I love the mixed berry filling in these Berry Oatmeal Crumble Bars, but feel free to adapt:

• Single Berry Filling: Use all blueberries, all raspberries, all strawberries (chopped), or all blackberries.
• Add Nuts: Mix chopped pecans or walnuts into the crumble topping mixture before sprinkling it on top.
• Add Citrus Zest: Add the zest of one lemon or orange to the crust/crumble mixture for extra brightness.
• Different Spices: Add a pinch of ginger or cardamom along with the cinnamon.
• Make it Vegan: Use a flax egg (1 tbsp ground flax + 3 tbsp water, let sit 5 mins) instead of the regular egg, and ensure your butter substitute (if using instead of coconut oil) is vegan.
• Make it Gluten-Free: Use certified gluten-free rolled oats and substitute a quality 1-to-1 gluten-free baking blend for the whole wheat pastry flour.

How to Make Berry Oatmeal Crumble Bars

Making these Berry Oatmeal Crumble Bars is super easy! Let me show you:

Prep Oven and Pan

1. First, I preheat my oven to 350°F (175°C).
2. I spray an 8×8 inch glass baking dish (or metal pan) with nonstick spray. I sometimes line it with parchment paper too, leaving an overhang, for super easy removal. I set the prepared pan aside.

Make the Crust/Crumble Mixture

1. In a medium bowl, I combine the dry ingredients for the crumble: the flour (whole wheat pastry or substitute), oats, baking powder, cinnamon, and salt. I whisk them together.
2. In a separate bowl, I whisk together the wet ingredients: the egg, brown sugar, vanilla extract, and melted (and slightly cooled) coconut oil until smooth.
3. I add the dry ingredients to the wet ingredients and stir with a rubber spatula or wooden spoon until the mixture turns into a thick, crumbly dough.
4. I press about two-thirds (⅔) of this mixture firmly and evenly into the bottom of the prepared pan to form the crust.
5. I set aside the remaining one-third (⅓) of the mixture for the topping.

Prepare the Berry Filling

1. In a medium bowl, I combine the mixed berries (fresh or frozen – no need to thaw if frozen!), cornstarch, fresh lemon juice, and pure maple syrup.
2. I gently stir until the berries are evenly coated and the cornstarch is mostly dissolved.

Assemble and Bake

1. I pour the prepared berry filling, including any juices, evenly over the pressed crust in the pan. I use a spoon or spatula to spread it out.
2. I take the remaining one-third of the crust/crumble mixture that I set aside earlier and crumble it evenly over the top of the berry layer.
3. I bake for 25-50 minutes (this is a large range, likely 30-40 minutes is more typical for an 8×8 pan – start checking around 25-30 mins). The bars are ready when the crust and crumble topping are golden brown around the edges and the berry filling is bubbly.

Cool Completely and Serve

1. The most important step for clean slices: I let the bars cool completely in the pan on a wire rack before cutting! This allows the berry filling to fully set. (Unless, of course, you want to serve them warm and gooey with vanilla ice cream!)
2. Once cool, I use the parchment overhangs (if used) to lift the bars out, or carefully cut them directly in the pan into 9 squares (or smaller/larger bars).
3. Serve!

Tips and Tricks for the BEST Crumble Bars

Here are my secrets for making perfect Berry Oatmeal Crumble Bars:

• Use Rolled Oats: Old-fashioned rolled oats provide the best chewy texture for the crust and crumble. Quick oats might make it softer.  
• Don’t Overmix Crust: Mix the crust/crumble just until combined for a tender texture.
• Coat Berries Well: Ensure the berries are evenly coated with the cornstarch mixture to help the filling thicken properly.
• Cool Completely: Patience is key! Letting the bars cool fully allows the filling to set properly for neat slicing. Chilling them briefly after cooling can help even more.
• Parchment Paper Sling: Highly recommended for easy removal from the pan, especially with a potentially sticky fruit filling.

How to Serve

These Berry Oatmeal Crumble Bars are fantastic served:

• As Is: Perfect for a healthy-ish breakfast, snack, or dessert.
• Warmed with Ice Cream: Gently warm a bar and top with vanilla bean ice cream for a decadent dessert.
• With Yogurt: Crumble over plain or vanilla Greek yogurt for breakfast or a snack.
• Packed for Lunch: A great addition to lunchboxes.

Serve warm or at room temperature.

Make Ahead and Storage

These bars store well, making them great for prepping ahead!

• Storage: Once completely cooled and cut, store the Berry Oatmeal Crumble Bars in an airtight container at room temperature for up to 3 days, or in the refrigerator for up to 5 days (they will be firmer from the fridge). Layer with parchment paper if stacking.
• Freezing: These bars freeze beautifully! Wrap individual bars or the whole slab tightly and store in a freezer-safe container or bag for up to 3 months. Thaw at room temperature or in the refrigerator.

FAQs about Berry Oatmeal Crumble Bars

• Can I use fresh berries instead of frozen (or vice versa)?
  • Yes! Both fresh and frozen berries work well in the filling. If using frozen, there’s no need to thaw them first; they’ll release their juices while baking.
• Can I make these gluten-free?
  • Easily! Use certified gluten-free rolled oats and substitute a quality 1-to-1 gluten-free baking blend for the whole wheat pastry/all-purpose flour.
• Can I use a different sweetener?
  • Yes, you could substitute honey for maple syrup in the filling (if not vegan). You could potentially use granulated sugar, but maple syrup adds nice flavor. Adjust amount to taste.

Enjoy these wholesome, delicious, and easy-to-make Berry Oatmeal Crumble Bars! They’re a perfect way to enjoy berries.

Berry Oatmeal Crumble Bars

• Author: Caoimhe Byrne
• Prep Time: 20 minutes
• Cook Time: 30 minutes
• Total Time: 50 minutes
• Yield: 9 1x
• Category: Dessert, Breakfast, Brunch, Snack, Bars, Baking
• Cuisine: American

Print Recipe

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Description

These berry oatmeal crumble bars are the perfect healthy dessert, snack, or even breakfast! An oat crumble doubles as the crust and topping, sandwiching a juicy mixed berry filling. A wonderful way to use up summer berries!

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Ingredients

Scale 1x2x3x

For the Oat Crust/Crumble Mixture:

• 1 cup plus 1 tablespoon (135g) whole wheat pastry flour (or all-purpose flour)
• 3/4 cup old-fashioned rolled oats (use certified gluten-free if needed)
• 1/2 teaspoon baking powder
• 1/2 teaspoon ground cinnamon
• 1/2 teaspoon salt
• 1 large egg, room temperature
• 1/3 cup packed light brown sugar
• 2 teaspoons vanilla extract
• 1/2 cup (118ml) coconut oil, melted and cooled slightly (or melted unsalted butter)

For the Berry Filling:

• 2 1/2 cups mixed berries (fresh or frozen – such as blueberries, raspberries, blackberries)
• 1 tablespoon cornstarch
• 1 tablespoon freshly squeezed lemon juice (from about 1/2 lemon)
• 2 tablespoons pure maple syrup

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Instructions

• Preheat Oven and Prepare Pan: Preheat oven to 350°F (175°C). Spray an 8×8 inch glass or metal baking dish with nonstick spray. Lining with parchment paper, leaving an overhang, is recommended for easy removal. Set aside.
• Make Crust/Crumble Mixture:
  • Combine Dry: In a medium bowl, whisk together the flour, oats, baking powder, cinnamon, and salt.
  • Combine Wet: In a separate large bowl, whisk together the egg, brown sugar, vanilla extract, and melted (slightly cooled) coconut oil until smooth.
  • Combine Wet & Dry: Add the dry ingredients to the wet ingredients. Stir with a rubber spatula or wooden spoon until the mixture turns into a thick, crumbly dough.
• Form Base Crust: Reserve about 3/4 to 1 cup of the dough mixture for the topping. Press the remaining (larger portion) dough firmly and evenly into the bottom of the prepared pan to form the crust.
• Make Berry Filling: In a medium bowl, combine the mixed berries (fresh or frozen), cornstarch, lemon juice, and maple syrup. Stir gently until the berries are evenly coated and the cornstarch is mostly dissolved.
• Assemble Bars: Pour the berry filling evenly over the pressed crust. Crumble the reserved dough mixture evenly over the top of the berry layer.
• Bake: Bake for 30-35 minutes, or until the crust is golden brown on the edges and the topping is lightly golden and set. (Original recipe notes 25-50 min; start checking around 30 min).
• Cool Completely: Let the bars cool completely in the pan on a wire rack before cutting. This is crucial for the filling to set properly and for clean slices. (Unless serving warm with ice cream, allow at least 1-2 hours cooling).
• Serve: Once completely cool, use the parchment paper overhang to lift the bars out of the pan. Cut into 9 squares (or desired size). Serve as is, or warm slightly and serve with vanilla ice cream.

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Notes

• Flour: Whole wheat pastry flour yields a tenderer crumb than regular whole wheat. All-purpose flour can be substituted 1:1.
• Berries: Use fresh or frozen berries. Do not thaw frozen berries before using; the baking time might be slightly longer.
• Coconut Oil: Melted butter (unsalted) can be substituted for coconut oil.
• Cooling: Allowing the bars to cool completely is very important for the filling to set and to prevent crumbling when cutting.
• Storage: Store cooled bars in an airtight container at room temperature for up to 3 days or in the refrigerator for up to 5 days.