Why You’ll Love Old Fashioned Oatmeal Rhubarb Bars Recipe
I love this recipe because it balances sweetness and tartness beautifully. The rhubarb cooks into a jammy filling that pairs perfectly with the chewy oatmeal base and crumbly topping. It’s an easy, reliable treat for potlucks, picnics, or a simple afternoon snack, and it requires nothing fussy—just classic ingredients that come together into something wonderful.
Ingredients
(Note: All ingredient amounts are listed in the recipe card below.)
For the base and topping: 3 cups old fashioned rolled oats 1 1/2 cups all-purpose flour 1 cup packed brown sugar 1 1/4 cups (2 1/4 sticks) unsalted butter, softened to room temperature 1/2 teaspoon salt 1/2 teaspoon baking soda
Directions
I combine the chopped rhubarb, sugar, cornstarch, and about a tablespoon of water in a saucepan. I bring the mixture to a simmer over medium-high heat, stirring frequently. I let it cook for 5–10 minutes until it becomes thick and jam-like and the rhubarb has softened.
I remove the saucepan from the heat, stir in the vanilla extract, and let the mixture cool for about 10 minutes so it thickens slightly and is no longer hot.
I heat the oven to 350°F and line a 9 × 11-inch baking pan with parchment or a silpat, lightly spraying it with baking spray.
In a medium bowl, I combine the oats, flour, brown sugar, butter, salt, and baking soda. I mix until coarse crumbs form.
I press all but 1 cup of the oat mixture firmly into the bottom of the prepared pan, making sure there are no cracks.
I pour the warm rhubarb filling evenly over the base, then sprinkle the remaining oat crumbs over the top.
I bake for 30–40 minutes, until the bottom is golden and the topping and filling have set.
I cool the bars completely before slicing so they hold their shape.
I sometimes add a pinch of cinnamon to the oat mixture for warmth. When I want extra texture, I fold in a handful of chopped pecans or almonds. If I’m craving a little brightness, I add a teaspoon of lemon zest to the filling. These bars also work beautifully with a mix of rhubarb and strawberries for a sweeter, more summery twist.
Storage/Reheating
I store leftovers in an airtight container at room temperature for up to 2 days or refrigerate them for up to 5 days. They also freeze very well; I wrap individual bars and store them for up to 2 months. To serve, I thaw them at room temperature or warm them briefly in the microwave for a softer texture.
FAQs
Can I use frozen rhubarb?
Yes, I use frozen rhubarb often. I don’t thaw it fully—just cook it a bit longer until the mixture thickens.
Why is my filling too runny?
The mixture likely didn’t cook long enough; I simmer until it reaches a thick, jammy consistency.
Can I reduce the sugar?
Yes, but the bars will be more tart. I usually reduce by no more than 1/4 cup.
Can I add fruit like strawberries?
Absolutely—strawberries pair beautifully with rhubarb.
Can I use quick oats?
I prefer rolled oats because they give a better texture, but quick oats can work in a pinch.
How do I keep the crust from crumbling?
I press it firmly into the pan to create a solid base.
Can I make these gluten-free?
Yes, I use a cup-for-cup gluten-free flour blend and certified gluten-free oats.
Do the bars need to be refrigerated?
Not strictly, but refrigeration keeps them firmer and extends their shelf life.
Can I double the recipe?
Yes, I bake it in a larger pan or two 9 × 11 pans.
How do I cut clean squares?
I cool the bars completely and use a sharp knife wiped clean between slices.
Conclusion
I love how these oatmeal rhubarb bars deliver nostalgic flavor with minimal effort. The buttery oat layers and tangy rhubarb filling create a dessert that feels both homey and satisfying. Whether I’m baking for a gathering or simply enjoying a quiet treat, these bars always feel just right.
Rustic, comforting oatmeal rhubarb bars with a jammy tart filling and a buttery oat crust and crumble. A timeless, not-too-sweet treat perfect for sharing.
Ingredients
Rhubarb Filling:
3 cups chopped rhubarb
1 1/2 cups granulated sugar
2 heaping tablespoons cornstarch
1 teaspoon vanilla extract
Base and Topping:
3 cups old fashioned rolled oats
1 1/2 cups all-purpose flour
1 cup packed brown sugar
1 1/4 cups (2 1/4 sticks) unsalted butter, softened to room temperature
1/2 teaspoon salt
1/2 teaspoon baking soda
Instructions
Combine rhubarb, sugar, cornstarch, and about 1 tablespoon water in a saucepan. Bring to a simmer over medium-high heat, stirring frequently.
Cook 5–10 minutes until thick, jammy, and the rhubarb has softened. Remove from heat, stir in vanilla, and let cool 10 minutes.
Heat oven to 350°F (175°C). Line a 9×11-inch pan with parchment or a silpat and lightly spray with baking spray.
Mix oats, flour, brown sugar, softened butter, salt, and baking soda in a bowl until coarse crumbs form.
Press all but 1 cup of the oat mixture firmly into the bottom of the pan.
Spread the warm rhubarb filling evenly over the base.
Sprinkle the remaining oat crumbs on top.
Bake 30–40 minutes until the bottom is golden and the topping is set.
Cool completely before slicing.
Notes
Add a pinch of cinnamon to the oat mixture for warmth.
Fold in chopped pecans or almonds for more texture.
Add lemon zest to the filling for brightness.
Use a mix of rhubarb and strawberries for a summery variation.
