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A white plate holds a square Blueberry-Rhubarb Crumble Bar topped with a scoop of vanilla ice cream and fresh mint, with a colorful cloth in the background.

Blueberry-Rhubarb Crumble Bars

Chef Jenn
These Blueberry-Rhubarb Crumble Bars are fruity, jammy, and layered with a buttery oat crumble. They’re perfect for brunch, snacks, or a sweet finish to any summer meal.
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Prep Time 45 minutes
Chill Time 2 hours 45 minutes
Total Time 3 hours 30 minutes
Course Dessert
Cuisine American
Servings 12 bars
Calories 380 kcal

Equipment

Ingredients
  

For the Blueberry-Rhubarb Filling:

  • 1 ½ cups rhubarb sliced
  • 6 ounces blueberries
  • ½ cup brown sugar packed
  • 2 tablespoons cornstarch
  • 2 tablespoons lemon juice
  • 1 tablespoon lemon zest
  • 1 teaspoon cinnamon

For The Crumble:

  • 1 ¼ cups old fashioned oats
  • 1 ⅔ cups all-purpose flour
  • 1 cup brown sugar lightly packed
  • 1/2 teaspoon baking powder
  • ¾ cups unsalted butter softened
  • 1/4 teaspoon salt

Instructions
 

  • Combine the rhubarb, blueberries, brown sugar, cornstarch, cinnamon, lemon juice, and zest in a saucepan. Cook over medium-low heat for about 15 minutes until thick and jammy. Let cool slightly.
  • Preheat the oven to 350°F and line a square baking pan with parchment paper.
  • In a large bowl, stir together the oats, flour, brown sugar, baking powder, and salt.
  • Add the cubed butter and mix with clean fingers or a pastry cutter until crumbly. Set 1 ½ cups of the crumble aside for the topping.
  • Press the remaining mixture into the prepared pan with an offset spatula and bake for 10 minutes.
  • Spread the filling over the base, then top with the reserved crumble.
  • Bake for 25–30 minutes, or until golden brown and bubbling.
  • Cool completely, then refrigerate for 2–3 hours before slicing.

Notes

Chef Jenn’s Tips

  • Use fresh rhubarb if it’s in season, but frozen works beautifully too; just don’t thaw it first.
  • Chill the bars before slicing! Trust me, this is the key to neat, bakery-worthy squares.
  • Add a dash of cardamom or ginger to the filling if you want to spice it up a bit.
  • Want extra crunch? Toss a few chopped walnuts or pecans into the crumble topping.

Nutrition

Serving: 1barCalories: 380kcalCarbohydrates: 61gProtein: 5gFat: 13gSaturated Fat: 8gPolyunsaturated Fat: 1gMonounsaturated Fat: 3gTrans Fat: 0.5gCholesterol: 31mgSodium: 78mgPotassium: 207mgFiber: 4gSugar: 29gVitamin A: 379IUVitamin C: 4mgCalcium: 68mgIron: 2mg
Keyword blueberry dessert, fruit bars, jam bars, oat crumble, rhubarb crumble bars
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