Mixed Berry Crumble Bars Recipe with Oat Streusel Topping

These Mixed Berry Oat Bars are a perfectly crumbly treat—loaded with berries, oats, a hint of cinnamon, and only about 10 minutes of prep. They work as a dessert or a special brunch item everyone will love.

This recipe was originally published June 2016 and updated March 2023.

Mixed Berry Oat Bars are ideal for summer, and thanks to frozen berries they’re just as good year-round. The buttery, crumbly oat topping is the highlight here—more crumble in every bite makes these bars irresistible.

If you love fruit and oats, these bars make a great treat or a special breakfast option. They’re similar in spirit to other favorites like strawberry crumble or apple crumble bars but with a bright mixed-berry filling.

Why You Will Love These Oatmeal Berry Bars:

• Quick prep: About 10 minutes to assemble—melt butter, mix the oat crumble, sweeten the berries, and press into the pan.
• Berry-packed: Use any combination you like—blueberries, raspberries, blackberries, and strawberries all work well.
• Gluten-free option: Use certified gluten-free quick oats and a 1:1 gluten-free all-purpose flour to make these bars gluten free.
• Versatile serving: Great for dessert, brunch, or a snack—serve warm or chilled, with ice cream or whipped cream if desired.
• Freezer friendly: Freeze individual bars for up to three months for a quick treat later.

Recipe Ingredients:

• Oats: Quick oats are preferred for better bar structure, though rolled oats will work.
• Flour: All-purpose flour for best texture; substitute a 1:1 gluten-free flour if needed.
• Brown sugar: Light brown sugar is used; dark brown is acceptable but will alter the flavor.
• Cinnamon: Adds warm spice—optional pinch of nutmeg if you like.
• Baking powder: Ensure it’s fresh for the best rise.
• Salt: Sea salt or table salt. If using salted butter, reduce the added salt by half.
• Vanilla: Vanilla extract for depth of flavor.
• Butter: Unsalted, melted and cooled (or use salted and reduce added salt).
• Berries: Any mix of fresh or frozen berries (thaw frozen before using).
• Lemon juice: Freshly squeezed brightens the filling; optional lemon zest.
• Sugar: Granulated sugar to sweeten the berries—adjust to taste.
• Cornstarch: Helps thicken the berry filling; substitute a little flour if needed.

How To Make These Berry Bars:

• Mix the berries, cornstarch, sugar, and lemon juice in a bowl and set aside. If using frozen berries, thaw first.
• In a separate bowl, whisk together oats, flour, brown sugar, cinnamon, baking powder, and salt.
• Add the melted butter and vanilla to the oat mixture and stir until crumbly.
• Line an 8×8-inch pan with parchment and press about two-thirds of the oat mixture firmly into the pan.
• Spread the berry mixture evenly over the pressed oats, then sprinkle the remaining oat mixture on top.
• Bake at 350°F for 28–32 minutes, until the berries are bubbling and the oat topping is golden brown. Cool completely before cutting.

• After baking, let the bars cool fully so the filling sets. For cleaner slices, chill for several hours and run a knife under hot water and dry between cuts.
• Serve warm with vanilla ice cream or cold with whipped cream. They also work broken into pieces over yogurt or in parfaits.

Storage Instructions:

Store the bars in an airtight container in the refrigerator for up to one week. Let them sit at room temperature for about 15 minutes before serving, or warm briefly in the microwave.

To freeze: cool completely, slice if desired, and wrap individually or place in a freezer-safe container for up to three months.

Other Desserts to Try:

• Zucchini Bars
• Apple Cranberry Crisp
• No Bake Cookie Butter Cookies
• Nutella Crumble Bars
• Peanut Butter Oatmeal Balls
• No Bake Double Chocolate Raspberry Crumble Bars
• Coconut Almond Chocolate Chunk Skillet Cookie

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