Can I use frozen rhubarb?

Yes. Thaw and drain it well before adding it to the bars.

How do I know the custard is set?

The center should jiggle slightly but not look liquid when the pan is gently moved.

Can I make these gluten-free?

Use a cup-for-cup gluten-free flour blend and certified gluten-free oats.

Why are my bars hard to slice?

They may still be warm. Cool completely, then chill briefly for the neatest cuts.

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Pies & Tarts

Rhubarb Custard Crumble Bars

Name: Rhubarb Custard Crumble Bars
Prep time: 25 min
Cook time: 42 min
Total time: 67 min
Yield: 16 servings
Cuisine: American
Ingredients: 1 1/2 cups all-purpose flour; 1 cup rolled oats; 3/4 cup sugar, divided; 1/2 teaspoon cinnamon; 1/2 teaspoon kosher salt; 3/4 cup cold butter, cubed; 2 cups chopped rhubarb; 2 large eggs; 1/2 cup milk; 1 teaspoon vanilla extract; 1 tablespoon cornstarch

By Beginnerbakes Test KitchenReviewed by Beginnerbakes Editorial TeamPublished Jun 28, 2026

American 67 mins beginner-bakingrhubarbcustard-barscrumble-barsseasonal-dessertpinterest-trendsv2

Rhubarb Custard Crumble Bars layer buttery crust, vanilla custard, tart rhubarb, and golden oat crumble for an approachable seasonal bake.

Prep 25 min

Cook 42 min

Total 67 min

Servings 16

Difficulty easy

Cuisine American

Ingredients

Servings 16

1 1/2 cups all-purpose flour
1 cup rolled oats
3/4 cup sugar, divided
1/2 teaspoon cinnamon
1/2 teaspoon kosher salt
3/4 cup cold butter, cubed
2 cups chopped rhubarb
2 large eggs
1/2 cup milk
1 teaspoon vanilla extract
1 tablespoon cornstarch

Ingredients for Rhubarb Custard Crumble Bars

Instructions

Preheat the oven to 350 degrees F. Line a 9-inch square pan with parchment.
Mix flour, oats, 1/2 cup sugar, cinnamon, and salt. Cut in cold butter until crumbly.
Press two-thirds of the mixture into the pan and bake for 12 minutes.
Whisk eggs, milk, vanilla, cornstarch, and remaining sugar until smooth.
Scatter rhubarb over the crust, pour custard over it, and sprinkle with remaining crumble.
Bake for 28 to 30 minutes, until the center is set and the crumble is golden. Cool before slicing.

Rhubarb Custard Crumble Bars process image

Tips

Equipment Needed

Use a 9-inch square pan, parchment, a pastry cutter or fork, and a medium mixing bowl. Parchment overhang makes the cooled bars much easier to lift and slice.

Ingredient Prep Notes

Keep the butter cold so the crust and crumble bake up tender instead of greasy. Chop rhubarb into small even pieces so it softens before the custard sets.

Oven Note

Bake on the center rack and cool the bars fully before cutting. If the crumble browns early, tent the pan loosely with foil for the final minutes.

Easy Upgrade Ideas

Add orange zest to the custard or sliced strawberries with the rhubarb. A light dusting of powdered sugar makes the bars look bakery-ready.

Frequently Asked Questions

Can I use frozen rhubarb?: Yes. Thaw and drain it well before adding it to the bars.
How do I know the custard is set?: The center should jiggle slightly but not look liquid when the pan is gently moved.
Can I make these gluten-free?: Use a cup-for-cup gluten-free flour blend and certified gluten-free oats.
Why are my bars hard to slice?: They may still be warm. Cool completely, then chill briefly for the neatest cuts.

Ingredient Replacements

Use strawberries with rhubarb for a sweeter bar. Gluten-free measure-for-measure flour can replace all-purpose flour if the oats are certified gluten-free. Half-and-half can replace milk for a richer custard.

Storage and Reheating

Refrigerate bars in an airtight container for up to 4 days. Serve chilled or let stand at room temperature for 15 minutes.

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Rhubarb Custard Crumble Bars

Recipe Details

Ingredients

Instructions