These peach plum crumble bars are a simple and delicious way to use up ripe late-summer stone fruit. Juicy peaches and tart plums cook down into a jammy filling that gets sandwiched between a hearty oat and walnut crust and crumble topping. They’re very lightly sweetened with maple syrup and coconut sugar, letting the natural sweetness of the fruit do most of the work. They’re just as good for a breakfast treat or afternoon snack as they are for dessert!
P.S. These bars should be made a day ahead or first thing in the morning so they have time to chill in the fridge.
Ingredient highlight
Plums! These juicy late-summer stone fruits are rich in polyphenols, including anthocyanins that give red and purple varieties their deep color. Plums also provide vitamin C, potassium, and fiber, with much of the fiber and antioxidants found in the skin.
Servings 9 square bars
Prep Time 20 minutes 
Cook Time 1 hour Ingredients
For the crust and crumble:
- 5 tbsp (71g) butter, melted
- 2 tbsp (40g) maple syrup
- 2 tbsp (20g) coconut sugar
- 1 tsp vanilla extract
- 1½ cups (162g) rolled oats
- 1½ cups (153g) raw walnuts
- ½ tsp kosher salt
For the filling:
- 1 lb peaches, pitted and chopped (about 2½ cups*)
- 1 – 2 tbsp maple syrup, depending on the sweetness of the fruit (optional)
- 2 tbsp tapioca starch (or cornstarch)
To serve:
- Whipped cream, whipped yogurt, plain yogurt, or vanilla bean ice cream (optional)
- *You need 4 cups of chopped fruit. The peach/plum mix is my favorite, but you could use all plums or all peaches. If using all peaches, add 1 tablespoon of lemon juice to give the filling enough tartness. If using all plums, be sure to add in the maple syrup for sweetness.
Instructions
- Preheat the oven to 350°F. Line a standard 8×8 or 9×9-inch baking dish with parchment paper.
- To a medium-large microwavable bowl, add the butter and microwave until just melted. Stir in the maple syrup, coconut sugar, and vanilla until combined.
- To a high-speed blender or food processor, add the oats and pulse into a coarse flour. Add the walnuts and pulse/blend again into a coarse flour. You want a crumbly meal with some texture remaining — don’t process it into a fine flour. Transfer to the bowl with the butter mixture. Add the salt and mix until thoroughly combined.
- Reserve 1 cup of the crust mixture to use for the crumble topping. Transfer the remaining mixture to the prepared baking dish and press it into an even, compact layer. Bake for 15 minutes.
- Meanwhile, in the same bowl you used to make the crumble, add the peaches, plums, starch, and sweetener (if using). Use your hands to gently toss to combine.
- Spread the peach-plum filling evenly over the prebaked crust. Crumble the reserved crust mixture evenly over the top.
- Bake for 40–45 minutes, or until the filling is bubbling around the edges and the crumble topping is deeply golden brown in spots. It is better to slightly overbake these than underbake them, but watch that the topping doesn’t burn.
- Allow the bars to cool completely in the baking dish, then transfer the baking dish to the fridge for at least 2 hours or overnight. Chilling the bars helps everything solidify and slice more easily. Slice into 9 squares.
- Serve them as is or with your creamy topping of choice.
Items you can prep ahead (optional)
- Make the crumble/crust mixture
- Pit and chop 4 cups worth peaches and plums
- Make and bake the bars up to 2 days ahead
Substitutions:
- To make vegan, replace butter with 4-4.5 tablespoons coconut oil. Star with 4 tablespoons. If the mixture feels dry, add some more.
- To make nut free, replace walnuts with pumpkin seeds. Add an extra tablespoon of butter to the mix (pumpkin seeds don’t have as much fat as walnuts).
Storage:
- Store leftovers in an airtight container in the fridge for up to 6 days or freeze for up to 2 months.
Leftovers + Repurposing:
- Eat these straight out of the fridge or let them sit out a bit to come to room temp if you want a softer texture.
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