Rhubarb Crumble Bars Recipe for a Simple Spring Dessert

By:

Ruby Bennett

Published:

June 6, 2026

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Why Are Rhubarb Crumble Bars a Must Try?

If you have never baked with rhubarb before, these easy Rhubarb Crumble Bars are the perfect place to start. Rhubarb is a vegetable often used in desserts for its tart flavor, and it shines in this recipe during its peak season from April through June. Here is why you will love making them:

Sweet and tart flavor pairing. The tangy rhubarb filling balances beautifully with a buttery shortbread crust and a crisp oat crumble topping.
Quick and simple preparation. The whole process takes about an hour, and most of that is hands off baking time.
Easy to customize. Swap in strawberries, add spices, or make them gluten free or vegan with simple substitutions.
Crowd pleasing dessert. These bars disappear fast at potlucks, picnics, and spring gatherings.
Serve warm or cool. Enjoy them with a scoop of vanilla ice cream or a dollop of whipped cream for an extra treat.

Whether you are a seasoned baker or just starting out, this recipe gives you a reliable, delicious result every time.

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Rhubarb Crumble Bars Ingredients

You will need two sets of ingredients: one for the filling and one for the crust and crumble topping. The same butter, flour, and oat mixture forms both the shortbread base and the crumble on top.

Ingredient	Amount	Notes & Substitutions
Fresh or frozen rhubarb	4 cups (chopped)	If frozen, thaw and drain excess liquid. Replace half with strawberries for a strawberry rhubarb version.
Granulated sugar	1 cup	Brown sugar adds a deeper flavor. For less sweetness, reduce to 3/4 cup.
Lemon zest	1 tablespoon	Lime zest works well for a citrus twist.
Lemon juice	1 tablespoon	Freshly squeezed is best. Lime juice can be used instead.
Cornstarch	2 tablespoons	Arrowroot or tapioca starch are good substitutes.
All purpose flour (for crust/topping)	1 cup	A gluten free blend works; add 1/4 tsp xanthan gum if not in the blend.
Rolled oats	1 cup	Use old fashioned rolled oats for the best texture. Quick oats are okay but will be less hearty.
Cold butter	1/2 cup (1 stick)	For the dough, use softened butter; for the crumble, use cold butter cut into small pieces. Vegan butter works.
Large egg	1	Flax egg (1 tbsp flaxseed meal + 3 tbsp water) for a vegan version.

Step by Step Instructions for Rhubarb Crumble Bars

Preheat your oven to 400°F (200°C). Grease a 9 inch square baking pan or line it with parchment paper, leaving overhang on two sides for easy removal.
Make the crust and crumble base: In a bowl, mix 1 cup flour, 1 cup oats, and a pinch of salt. Rub in 1/2 cup softened butter until the mixture looks like coarse crumbs. Add the egg and stir until a soft dough forms.
Press two thirds of the dough evenly into the bottom of the prepared pan. Bake for 15 minutes, until the edges are lightly golden. Set aside to cool slightly.
While the crust bakes, prepare the filling: In a saucepan, combine 4 cups chopped rhubarb, 1 cup sugar, lemon zest, and lemon juice. Cook over medium heat for 5 7 minutes, stirring occasionally, until the rhubarb softens and the mixture begins to bubble.
Stir in 2 tablespoons cornstarch. Continue cooking for another 5 minutes, stirring constantly, until the filling thickens and becomes glossy. Remove from heat.
Pour the warm rhubarb filling over the pre baked crust and spread it evenly.
For the crumble topping: Take the remaining dough and add a few extra tablespoons of cold butter (cut into small cubes). Rub the butter into the dough until it forms coarse, crumbly pieces. You can also add 1/4 cup chopped nuts or 1/2 teaspoon cinnamon at this point.
Sprinkle the crumble topping evenly over the rhubarb filling. Bake for 20 25 minutes, until the topping is golden brown and the filling is bubbling around the edges.
Cool the bars completely in the pan on a wire rack for at least 1 2 hours. This step is crucial for clean slices. Once cool, lift the bars out using the parchment overhang and cut into 9 squares.

Make Ahead Options

Busy schedule? You can prepare the components in advance. The crust and crumble topping can be made up to 24 hours ahead and stored separately in airtight containers in the refrigerator. The rhubarb filling can be made up to 3 days ahead and kept chilled. When you are ready, simply assemble and bake as directed. Cool completely before cutting. This make ahead strategy saves time without sacrificing taste or texture.

Rhubarb Crumble Bars Variations

Once you master the basic recipe, try these creative twists:

Strawberry Rhubarb: Replace half the rhubarb with chopped fresh or frozen strawberries.
Lime Citrus: Use lime zest and lime juice instead of lemon for a bright, zesty flavor.
Gluten Free: Swap the all purpose flour with a gluten free 1 to 1 baking blend and ensure your oats are certified gluten free.
Nutty Crunch: Add 1/4 cup crushed almonds or walnuts to the crumble topping.
Spiced: Mix 1/2 teaspoon cinnamon or nutmeg into the crumble or the filling.
Vegan: Use vegan butter and a flax egg (1 tbsp flaxseed meal + 3 tbsp water).
Spicy Kick: Add a pinch of cayenne pepper to the filling for a surprising heat.
Berry Blend: Mix in 1/2 cup blueberries or raspberries with the rhubarb for extra color and flavor.

For another take on rhubarb desserts, try our Rhubarb Crumble Cheesecake Bars for a creamy, tangy twist.

Expert Tips for Rhubarb Crumble Bars

Avoid slicing warm bars. Let them cool completely for at least 2 hours so the layers set firmly. Cutting too early leads to messy, runny pieces.

Prevent a soggy crust: Pre bake the shortbread crust for 15 minutes before adding the filling. Also, toss the rhubarb with cornstarch and let it sit for 15 minutes before cooking to help absorb excess moisture.
Keep butter cold for the crumble: For a crisp, crumbly topping, use cold butter and do not overmix. Your fingers should still see small butter pieces.
Customize your topping: Add crushed nuts, cinnamon, or a handful of coconut flakes to the crumble for extra texture.
Storage: Store leftovers in an airtight container at room temperature for up to 2 days, or in the refrigerator for up to 5 days.

Looking for another oat topped favorite? Check out our Amish Oatmeal Rhubarb Bars With Crumb Topping for a rustic, old fashioned version.

What to Serve with Homemade Rhubarb Crumble Bars

These bars are delicious on their own, but pairing them with the right beverage or accompaniment takes them to the next level. Here are seven ideas:

Vanilla ice cream, The classic choice. The creamy, cold vanilla contrasts the warm, tangy rhubarb.
Whipped cream, Light and airy, it adds a gentle sweetness without overpowering.
Hot coffee, A rich, robust coffee balances the tartness.
Mint tea, Refreshing and herbal, it cleanses the palate between bites.
Mixed berry compote, Spoon extra berries over the top for even more fruitiness.
Nuts and dark chocolate, Add crunch and a touch of bittersweet decadence.
Sparkling lemonade, Citrusy bubbles harmonize with the lemon notes in the bars.

How to Store and Freeze Rhubarb Crumble Bars

Proper storage keeps your bars fresh and tasty for days or even months.

Room temperature: Keep in an airtight container for up to 2 days. The crumble will stay crisp.
Refrigerator: Store in a sealed container for up to 5 days. The filling will be firmer, and the bars are still delicious cold or reheated.
Freezer: Wrap individual bars tightly in plastic wrap, then place them in a freezer safe bag or container. Freeze for up to 3 months.
To reheat frozen bars: Thaw overnight in the refrigerator, then warm in a microwave for 20 30 seconds or in a 300°F oven for 10 minutes. Add a scoop of ice cream for that fresh from the oven experience.

Rhubarb Crumble Bars Recipe FAQs

How do you make rhubarb crumble bars?

Press a buttery shortbread crust into a pan and par bake it. Layer fresh rhubarb tossed with sugar and cornstarch on top, then sprinkle with an oat crumble mixture. Bake until the filling bubbles and the topping is golden.

Can I use frozen rhubarb in crumble bars?

Yes. Thaw the rhubarb first and drain off excess liquid. Toss with a little extra cornstarch to absorb moisture and prevent a watery filling.

How do I keep the crust from getting soggy?

Par bake the crust for about 10 minutes before adding the filling. Also, toss the rhubarb with cornstarch or flour to thicken the juices as it bakes.

How long do rhubarb crumble bars last?

Store them in an airtight container in the refrigerator for up to 4 days. Let them cool completely before covering to keep the topping crisp.

Can I freeze rhubarb crumble bars?

Yes. Cool the bars completely, then wrap tightly in plastic wrap and foil. Freeze for up to 3 months. Thaw in the refrigerator and reheat in a low oven to restore crispness.

What goes well with rhubarb crumble bars?

Serve them warm with a scoop of vanilla ice cream, a dollop of whipped cream, or a drizzle of custard. A dusting of powdered sugar also works well.