Rhubarb is one of my favorite fruits to bake with. (Yes, I know it’s technically a vegetable, but for baking intents and purposes, it’s treated like a fruit.)
This recipe is straight from my grandma’s recipe box, and nostalgia abounds. Anything rhubarb instantly reminds me of her and the backyard garden full of it, alongside raspberry bushes for miles and the fluffiest pink peonies. (She also made a mean applesauce, which was quite possibly more sugar than apples, and boy did I gobble it up at every visit. That applesauce was pure comfort in a canning jar.)
These rhubarb bars are buttery, sweet and a tad bit tangy. They’re also delightfully over the top served with a scoop of vanilla ice cream. Cheers, grandma! ❤️

Grandma Valita's Rhubarb Bars
- Prep Time: 20
- Cook Time: 30
- Total Time: 50 minutes
- Category: Bars
- Method: Baking
- Cuisine: American
Description
Makes ~16 bars, depending on how you slice them.
If enjoying over the course of more than a day or two, store in the refrigerator.
Ingredients
For the filling:
- 1 ½ cups granulated sugar (300 g)
- 2 TB cornstarch (16 g)
- 3 cups chopped rhubarb (from about 1 lb)
- ¼ cup water
- 1 tsp vanilla
For the bars:
- 1 ½ cups quick oats (120 g)
- 1 cup packed light brown sugar (213 g)
- 1 ½ cups all-purpose flour (180 g)
- ½ cup chopped walnuts (56 g) (optional, see note)
- ½ tsp baking soda
- ½ tsp fine-grain salt (like table or sea salt)
- 1 cup cold, unsalted butter (2 sticks, 8 oz)
Instructions
Preheat oven to 375F degrees
Butter a 9 x 13 pan and line the bottom with parchment
For the filling:
- In a medium saucepan, whisk together the cornstarch and sugar. Add in the rhubarb and water and stir until everything is well combined. Over medium heat, cook until the sugar is melted and soupy. Increase heat to medium-high and bring to a full boil. Stirring constantly, boil 1 - 2 minutes, until the the sauce is thickened, no longer cloudy, and the rhubarb has broken down. (The total time for making the filling is ~10 minutes.) Remove from the heat and stir in the vanilla. Set the filling aside while you make the bars.
For the bars:
- In a large bowl, stir together all the ingredients except the butter. Rub in the cold butter with your fingers, a pastry blender, or a fork until the mixture looks pebbly.
- To assemble, reserve 1 cup of the oat-flour mixture. Press the remaining mixture into the prepared pan. Top with the rhubarb filling (it will still be warm) and spread evenly. Then sprinkle with the reserved oat-flour mixture.
- Bake 30-35 minutes, until golden brown and the edges are bubbling. Let cool completely before slicing. These bars are equally delicious at room temperature or cold out of the fridge.
Notes
- I usually omit any nut called for in a baked good, 🤷 but walnuts really do pair beautifully with rhubarb. So for this recipe, I like to chop the walnuts extra, extra fine (so you get the flavor, but not the crunchy texture). And if I'm feeling especially fancy, I'll lightly toast the walnuts ahead of time.
Keywords: Rhubarb, Rhubarb Bars, Rhubarb Recipes, Old-Fashioned Recipes, Grandma Recipes, Spring Recipes, Summer Recipes
Maria
Grandma Valita's rhubarb bars were a huge hit at the workplace (even got the non-rhubarb fans to like rhubarb)! 🙂 This recipe is a keeper, thanks Sarah!
Sarah Marx Feldner
Maria: Thank you SO much for sharing these bars with your coworkers. How lucky they are to have you! xoxo 💕
Judy Martel
These bars are scrumptious! And not just because the rhubarb came from my garden 🙂 The crust is amazing. And I've tried a lot of different bars. Thank you for sharing them with me, and for sharing the recipe.
★★★★★
Sarah Marx Feldner
What a compliment, Judy! Thank you so much for the high praise - and the rhubarb! xoxo 💕