Rustic Plum Bars with Oat Crumble

Plum Bars are a delightful way to showcase fresh summer plums. With a crisp shortbread-like crust, a juicy plum filling, and a simple crumb topping, these bars make an easy, crowd-pleasing dessert for picnics, potlucks, or a relaxed afternoon at home.

Stone fruit season is one of the best times of year for baking. Plums may get less attention than peaches, but their sweet-tart flavor and tender flesh are perfect in a crumb bar. These plum bars follow a familiar crumb-bar formula: a buttery crust pressed into the pan, a lightly sweetened plum filling, and the remaining crumb mixture scattered on top to bake into a crisp, golden topping.

Ingredients

The short notes below clarify a few choices; the full ingredient list follows in the recipe section.

Flour – Use all-purpose flour for best texture. You can substitute a 1:1 gluten-free baking flour or white whole wheat if desired.

Sugar – Regular granulated sugar gives the right balance of sweetness. For a deeper, less sweet flavor, try coconut sugar, though the color will be darker.

Butter – Cold butter creates the tender shortbread crust and crumb topping. I don’t recommend replacing it with oils for this recipe unless you’re using a reliable vegan butter substitute.

Egg – One egg binds the crust; to make the recipe vegan, use a flax egg (1 tablespoon ground flaxseed mixed with 2.5 tablespoons water and rested until gelled).

Plums – Fresh, ripe plums work best. Any variety is fine; taste and sweetness vary slightly by variety so adjust sugar to taste if your plums are very sweet or very tart.

Instructions

Step 1: Prepare the crust and topping. Preheat the oven to 400°F (204°C). In a large bowl, whisk together the flour, sugar, baking powder, and salt. Grate the cold butter directly into the bowl using a cheese grater, or cut it into small cubes and rub it into the flour with your fingertips until the mixture resembles coarse crumbs or small pebbles. Stir in the whisked egg and the milk until the dough just comes together; it will still be crumbly.

Step 2: Make the plum filling. In a medium bowl, combine diced fresh plums with the sugar, a couple tablespoons of flour, and the vanilla extract. Toss gently so the fruit is evenly coated. Let the mixture sit briefly while you press the crust into the pan; this softens the plums slightly and helps them release a little juice during baking.

Step 3: Assemble the bars. Line an 8×8-inch (20×20 cm) baking pan with parchment paper, leaving an overhang for easy removal. Press about two-thirds of the crust mixture evenly into the bottom of the prepared pan to form a compact base. Spread the plum mixture over the crust in an even layer. Crumble the remaining crust mixture over the plums to create the topping.

Step 4: Bake and cool. Bake for 30–32 minutes, or until the edges are golden brown and the plum filling is bubbling slightly. Remove from the oven and allow the bars to cool completely in the pan on a wire rack. Cooling helps the filling set so the bars slice cleanly. Once cooled, lift the bars from the pan using the parchment overhang and cut into squares.

Variations and tips

• Spice it: Add 1/2 teaspoon freshly grated ginger or 1/4 teaspoon ground cinnamon to the plum filling for a warm, aromatic note (choose one).
• Swap the fruit: Diced peaches or apricots substitute beautifully for plums when in season.
• Make it vegan: Replace the egg with a flax egg and use a plant-based butter.
• Make it gluten-free: Use a 1:1 gluten-free baking flour blend.
• Serving suggestion: Serve bars at room temperature, or warm gently and pair with a scoop of vanilla ice cream for a classic combination.

Can I use frozen plums?

Yes. Thaw frozen plums completely and drain any excess liquid before using. If the fruit is very wet, toss it with an extra tablespoon of flour or cornstarch to help thicken the filling while baking.

Storage

Refrigerator: Store cooled bars in an airtight container in the refrigerator for up to one week. They keep well and are excellent for grab-and-go snacks.

Freezer: Freeze fully cooled bars in a freezer-safe container for up to two months. Separate layers with parchment or wax paper so the pieces don’t stick together. Thaw in the refrigerator or at room temperature before serving.

More summer dessert ideas

• Cherry crumb bars — similar crumb base with sweet-tart cherries.
• Strawberry cheesecake bars — creamy cheesecake layered with fresh strawberries.
• Strawberry crumb pie — a classic summer pie with a crunchy topping.

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