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Sliced strawberry rhubarb bars with a crumb topping on a dark slate board next to fresh berries and rhubarb.

Classic Rhubarb Crumb Bars

These delightful rhubarb bars feature a vibrant, tart rhubarb filling nestled between a buttery shortbread crust and a sweet, golden crumb topping. A perfect seasonal treat, easy to make and impossible to resist.
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Prep Time 30 minutes
Cook Time 50 minutes
Total Time 1 hour 20 minutes
Servings: 16 pieces
Course: Dessert, Snack
Cuisine: American
Calories: 310
Ingredients Equipment Method Notes

Ingredients
  

For the Crust and Crumb Topping
  • 2 cups All-purpose flour
  • 1 cup Granulated sugar
  • 1/2 tsp Salt
  • 1 cup Unsalted butter cold, cut into 1/2-inch cubes
  • 1/2 cup Old-fashioned rolled oats (optional, for topping)
For the Rhubarb Filling
  • 5 cups Fresh rhubarb trimmed and chopped into 1/2-inch pieces (about 1.5 lbs)
  • 1 cup Granulated sugar (adjust to taste based on rhubarb tartness)
  • 1/4 cup Cornstarch
  • 1 tbsp Fresh lemon juice
  • 1/4 cup Water (only if rhubarb is very dry, to prevent scorching)

Equipment

  • 9x13 inch baking pan
  • Large mixing bowls
  • Pastry Blender
  • Small Saucepan
  • Measuring cups and spoons

Method
 

Prepare for Baking
  1. Preheat your oven to 375°F (190°C). Lightly grease a 9x13 inch baking pan with butter or cooking spray.
Make the Crust and Topping
  1. In a large mixing bowl, combine the flour, 1 cup granulated sugar, and salt. Whisk briefly to combine.
  2. Add the cold, cubed butter to the dry ingredients. Using a pastry blender or your fingertips, cut the butter into the flour mixture until it resembles coarse crumbs. Be careful not to overmix; some larger pea-sized pieces are fine.
  3. Press about half of this crumb mixture evenly into the bottom of the prepared 9x13 inch baking pan. Reserve the other half for the topping. Bake the crust for 15 minutes, until lightly golden.
Prepare the Rhubarb Filling
  1. While the crust is pre-baking, combine the chopped rhubarb, 1 cup granulated sugar, cornstarch, and lemon juice in a medium saucepan. If your rhubarb seems very dry, add 1/4 cup of water to the mixture.
  2. Cook over medium heat, stirring frequently, for 5-7 minutes, or until the rhubarb softens slightly and the mixture begins to thicken. It should be bubbly and jam-like, but not fully cooked down.
Assemble and Bake the Bars
  1. Remove the pre-baked crust from the oven. Carefully pour the hot rhubarb filling evenly over the crust.
  2. If using, stir the optional rolled oats into the reserved half of the crumb mixture. Evenly sprinkle this crumb topping over the rhubarb filling.
  3. Return the pan to the oven and bake for another 30-35 minutes, or until the topping is golden brown and the filling is bubbly and set.
  4. Remove from the oven and place on a wire rack to cool COMPLETELY. This is crucial for the bars to set properly and be easy to cut. It may take 2-3 hours.
  5. Once cooled, cut into squares and serve. Enjoy your delicious rhubarb bars!

Notes

For best results, ensure the bars are fully cooled before cutting; otherwise, the filling may be too soft. Store leftover rhubarb bars in an airtight container at room temperature for up to 2 days, or in the refrigerator for up to 5 days. These bars also freeze well for up to 3 months.