Mixed Berry Crumble Bars Recipe for Juicy, Homemade Dessert

Enjoy the peak flavors of summer with these Mixed Berry Crumble Bars — an easy, crowd-pleasing treat bursting with bright, juicy berries and a buttery oat crumble. This recipe uses one simple mixture for both the base crust and the crumble topping, making the process quick and streamlined. A lightly sweetened blend of raspberries, blueberries and blackberries becomes a vibrant filling that complements the rich, slightly nutty crust. These bars are perfect for summer gatherings or to enjoy any time of year using frozen berries.

WHY YOU WILL LOVE THIS RECIPE:

• Easy to make – one dough mixture serves as both crust and topping, saving time and effort.
• Juicy triple-berry filling – raspberries, blackberries and blueberries blend tart and sweet notes for a lively filling.
• Buttery oat crumble – quick oats add texture while almond flour gives the crust a rich, aromatic finish.
• One-pan recipe – no pre-cooking of the filling is required. You simply combine the berries with sugar and jam, then spread over the baked base.

INGREDIENTS

• All-purpose flour – unbleached all-purpose flour works well for the crust and topping.
• Butter – unsalted or salted butter may be used; if using unsalted, add a small pinch of salt for balance.
• Vanilla extract – a touch of pure vanilla enhances the overall flavor.
• Brown sugar – packed light or dark brown sugar adds molasses-like depth and a caramel note.
• Granulated sugar – balances the tartness of the berries without overpowering them.
• Almond flour – ground almonds add richness and a subtle floral note to the crust.

• Oats – quick oats are preferred because they blend smoothly into the crumb and bake more evenly than old-fashioned rolled oats.
• Blueberries – fresh or frozen blueberries both work for the filling.
• Blackberries – fresh or frozen blackberries contribute depth and tartness.
• Raspberries – fresh raspberries are ideal; if using frozen, choose whole berries where possible to avoid excess mushiness.
• Cherry or strawberry preserves – a couple of tablespoons of jam intensify the berry flavor and add natural sweetness to the filling.

STEP BY STEP INSTRUCTIONS

• Step 1 — Make the base and topping. In a large bowl, combine the flour, oats, almond flour, brown sugar, baking powder and salt. Stir until evenly mixed with no lumps of brown sugar. Add cooled melted butter and mix until the dough holds together in moist clumps with no dry spots.
• Step 2 — Reserve the topping. Remove one-third of the crumb mixture and set it aside to use as the crumble topping.
• Step 3 — Form the base crust. Press the remaining two-thirds of the mixture evenly into a prepared 8-inch square pan lined with parchment. Use your hands and the bottom of a measuring cup to compact and level the crust. Bake until golden (about 12 minutes), then let it cool slightly.
• Step 4 — Make the filling. In a medium bowl, combine the berries with granulated sugar, flour and cornstarch until the fruit is evenly coated. Gently stir in the preserves.
• Step 5 — Top the bars. Spoon the filling evenly over the cooled crust. Crumble the reserved topping in large clumps over the berries.
• Step 6 — Bake. Bake for 30–35 minutes, until the topping is golden and the berry filling bubbles around the edges.
• Step 7 — Cool and chill. Transfer the pan to a wire rack and cool completely in the pan. Once cooled, cover and refrigerate for at least 2 hours to firm up before slicing.

EXPERT BAKING TIPS FOR BERRY CRUMBLE BARS

• Cool the melted butter. Let melted butter come to lukewarm or room temperature before adding so the crumb doesn’t become greasy.
• Don’t skip chilling. Chilling the bars after they cool ensures they hold together cleanly when sliced.
• Let the base cool slightly first. Allow the baked crust to cool before adding the filling to avoid a soggy bottom.

RECIPE FAQ

If you enjoy baking with berries, try more berry-forward treats from the same collection.

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Mixed Berry Crumble Bars

Christina Marsigliese

These bars feature a juicy triple-berry filling with a buttery brown-sugar oat crumble. They’re quicker than pie but deliver the same bright berry flavor — great for summer or when using frozen berries year-round.

Prep Time 10 mins

Cook Time 45 mins

Servings 16 squares

Ingredients

Crust and topping:

• 1 cup plus 2 tbsp (160g) all-purpose flour
• 2/3 cup (60g) quick oats
• 1/4 cup (25g) almond flour
• 1/2 cup (110g) packed light brown sugar
• 1/2 teaspoon baking powder
• 1/4 teaspoon salt
• 1/2 cup unsalted butter, melted and cooled

Triple Berry Filling:

• 1 cup (120g) blackberries, frozen or fresh
• 1 cup (120g) raspberries, frozen or fresh
• 1 cup (120g) blueberries, frozen or fresh
• 3 tablespoons (40g) granulated sugar
• 1 tablespoon (9g) all-purpose flour
• 1 tablespoon (8g) cornstarch
• 2 tablespoons (30ml) cherry or strawberry preserves

Instructions

• Preheat oven to 350°F. Line an 8-inch square pan with parchment paper, leaving an overhang for easy removal.
• Make the base and topping: combine flour, oats, almond flour, brown sugar, baking powder and salt. Add cooled melted butter and mix until the dough forms moist clumps. Reserve one-third for the topping.
• Press two-thirds of the mixture into the prepared pan and smooth with the bottom of a measuring cup. Bake for about 12 minutes, then cool slightly.
• Make the filling: toss berries with granulated sugar, flour and cornstarch. Stir in preserves, then spread the filling over the crust. Sprinkle the reserved crumb mixture in clumps on top.
• Bake 30–35 minutes until the crumble is golden and the filling bubbles. Cool completely on a wire rack, then refrigerate for at least 2 hours before slicing.