Old Fashioned Rhubarb Crisp [with Oatmeal]

Rhubarb is one of the first harvests in many regions, ripening in early spring. This rhubarb crisp recipe is a delicious way to use it while it’s in season! 

Originally published March 2023; this post has been updated.

rhubarb crisp in a white bowl, topped with a swirl of whipped cream.

 

Let’s start with what is rhubarb, exactly? A rhubarb plant is a long-lived perennial that grows on stalks — similar to celery, but much larger. The stalks range from pink to bright red. 

The stalks of rhubarb are edible; the leaves are poisonous, as they contain dangerous levels of oxalic acid. You’d need to eat a lot to kill you, but small amounts can make a person sick. 

The stalks are very tart, so you’ll often see rhubarb paired with strawberries to cut the tartness, and almost always in sweetened dishes like pie, cake, and jam — and this easy rhubarb crisp!

cover of Attainable Sustainable Pantry book, featuring numerous pantry items, collage style, on a light green background.Ready to DIY your pantry with more wholesome ingredients? Check out my new book from National Geographic! Attainable Sustainable Pantry is filled with delicious recipes for some of your favorite condiments, snacks, and toppings, along with an entire section on home food preservation. It’s the guide you need to start skipping packaged products and embrace homemade.

ingredients for rhubarb crisp recipe on a marble background.

Ingredients

Rhubarb — I use fresh rhubarb from the garden. It can often be found fresh at farmers markets during the spring months.

Flour When I bake with all-purpose flour I opt for the unbleached version. Bleached flour is very white, but it’s also treated with bleaching agents that I don’t really need in my food.

Rolled oats — They’re not just for breakfast! Old fashioned rolled oats give this crisp a delicious flavor. Optionally, you can pulse half the oats in a blender to make them a bit more fine.

Sugar — Use your favorite brand of granulated cane sugar. I prefer organic.

Cornstarch This is our thickener so the crisp isn’t watery.

chopped rhubarb on a wooden cutting board from above.

Making Old Fashioned Rhubarb Crisp

Combine the crisp ingredients, except rhubarb, and press half of the mixture into the pan as a “crust.”

3 panel showing the process of assembling the crisp.

Top with the sliced rhubarb in an even layer.

Cook the syrup in a saucepan to dissolved all of the ingredients before pouring over the rhubarb.

pot with sugar syrup and vanilla, from above.

 

Finally, top with the remaining crumb mixture.

Bake until brown and bubbly! Serve rhubarb crisp warm or at room temperature.

rhubarb crisp in a white baking dish with a serving scooped out in a wooden spoon.

FAQs

Can I use frozen rhubarb instead of fresh?

I haven’t tested that in this recipe. In general though, you will want to thaw and drain the frozen rhubarb to remove excess moisture. Because of the freezing process, the rhubarb will have “shrunk” some with water loss, so you may need to add more to completely cover the crust. You’d also want to think about using less sugar syrup to combat excess moisture. Let me know in the comments if you work this out!

Can I make this crisp gluten-free?

Pick up a cup-for-cup gluten-free all-purpose flour and you can use that instead of wheat flour. Make sure your oats are certified gluten-free if it’s critical that this rhubarb recipe is gluten free.

Can I make crisp ahead?

I recommend baking the day you are serving. It tastes best fresh from the oven and still slightly warm. It will still be crisp later that day and likely the following day, but beyond that it will become soggy. Still delicious for up to 4 days when stored in the fridge, but the texture will have changed.

rhubarb crisp in a white baking dish with a serving scooped out in a wooden spoon.

★ Did you make this recipe? Don’t forget to give it a star rating below! ★

rhubarb crisp in a white bowl, topped with a swirl of whipped cream.

Rhubarb Crisp

This classic rhubarb crisp has a lovely crunch topping and a sweet and tart filling.
4.75 from 63 votes
Print Pin Rate
Prep Time: 15 minutes
Cook Time: 30 minutes
Total Time: 45 minutes
Servings: 12 servings
Author: Claudie Evert

Ingredients

  • 4 cups rhubarb chopped
  • 1 ¼ cup all-purpose flour
  • 1 cup rolled oats
  • 1 ¼ cup brown sugar packed
  • ½ cup melted butter
  • 1 teaspoon ground cinnamon

For the sugar syrup:

  • 1 cup granulated sugar
  • 2 tablespoons cornstarch
  • 1 cup cold water
  • 1 teaspoon vanilla extract

Instructions

  • Use a fork or pastry blender to combine the flour, oats, cinnamon, brown sugar, and melted butter in a medium bowl until it's crumbly.
    1 1/4 cup all-purpose flour, 1 cup rolled oats, 1 1/4 cup brown sugar, 1 teaspoon ground cinnamon, 1/2 cup melted butter
  • Press one-half of the crumb mixture into a buttered 7"x11" or 8.5"x11" baking dish.
  • Spread the rhubarb slices evenly over the pressed crumb mixture.
    4 cups rhubarb
  • Make the sugar syrup: Whisk sugar, cornstarch, and water together in a small saucepan over medium-low heat. Cook until thick, clear, and bubbly, approximately 5-7 minutes.
    1 cup granulated sugar, 2 tablespoons cornstarch, 1 cup cold water
  • Remove from heat and whisk in vanilla. Pour the sugar syrup evenly over rhubarb.
    1 teaspoon vanilla extract
  • Crumble the remaining oat topping evenly over the rhubarb in the pan.
  • Bake at 350 degrees until edges are bubbling and the crumb topping is browned, about 30-40 minutes.

Notes

  • I used light brown sugar; dark brown sugar will provide a deeper molasses flavor if you prefer that.
  • Serve this easy dessert with a dollop of whipped cream or a scoop of vanilla ice cream.

Nutrition

Calories: 307kcal | Carbohydrates: 57g | Protein: 3g | Fat: 8g | Saturated Fat: 5g | Polyunsaturated Fat: 1g | Monounsaturated Fat: 2g | Trans Fat: 0.3g | Cholesterol: 20mg | Sodium: 71mg | Potassium: 190mg | Fiber: 2g | Sugar: 39g | Vitamin A: 278IU | Vitamin C: 3mg | Calcium: 64mg | Iron: 1mg
Did you make this recipe?Mention @attainablesustainable or tag #attainablesustainable!

 

Love rhubarb? Be sure to try this rhubarb coffee cake, too! 

rhubarb crisp in a glass baking dish.

Originally published February 2021; this post has been updated.

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About the author: Claudie Evert is passionate about living lightly on the earth. She digs in the garden, cooks food from scratch, and will — someday — master the art of picking out a ripe watermelon.

11 comments… add one
  • Marcia May 15, 2024 @ 7:40

    Made this recipe I would cut back some on the water I like my bars crispier than this recipe produces. My bars got soggy in fridge

    • Kris Bordessa, National Geographic author Jul 8, 2024 @ 15:44

      Thanks for the feedback.

  • Marcia May 13, 2024 @ 10:16

    Very good I did cut back a little on white sugar just the right amount of tartness

  • Sean Campbell Jul 14, 2023 @ 16:28

    When I was a kid rhubarb was everywhere. Not anymore. But I was lucky and found some tonite at the grocery store. Lost my recipe,so I looked online and this is the one that I remember. I’ll make it tomorrow and I can’t wait!

    • AttainableSustainable Jul 26, 2023 @ 7:10

      I hope you loved it!

  • Diana Jul 5, 2023 @ 3:00

    IT’s Rhubarb season! Easy and good way to use rhubarb! I made only half the recipe the first time. Tonight I’ll make the whole recipe for a party. Didn’t change a bit of the recipe.

    • AttainableSustainable Jul 5, 2023 @ 5:04

      I’m glad you liked it!

  • Lisa Green Jun 21, 2023 @ 11:38

    LOVED this recipe. I borrowed from a rhubarb tart recipe and added chopped raw pistachios to the crumb topping. Will definitely make again!

    • AttainableSustainable Jun 22, 2023 @ 5:55

      Great idea, sounds delicious!

  • Deb Jun 8, 2023 @ 6:59

    I like this recipe but next time, I will double the amount of rhubarb

    • AttainableSustainable Jun 8, 2023 @ 7:38

      Sounds good, thank you!

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