Rhubarb Oatmeal Bars

Rhubarb Oatmeal Bars are the perfect combination of tart fruit filling and a buttery, crumbly oat crust that I love baking when rhubarb season rolls around. They’re easy to make, great for sharing, and taste just as good warm with a scoop of ice cream as they do straight from the fridge the next day.

Why You’ll Love This Recipe

I love how these bars highlight the natural tang of rhubarb while balancing it with a lightly sweet, hearty oatmeal base. The texture is a perfect mix of soft fruit filling and a golden, crunchy topping. They’re simple, rustic, and always a hit at gatherings, bake sales, or just when I want a treat that’s a little different from the usual dessert lineup.

ingredients

(Here’s a tip: Check out the full list of ingredients and measurements in the recipe card below.)

For the crust and topping:
old-fashioned rolled oats
all-purpose flour
brown sugar
baking soda
salt
unsalted butter, melted

For the filling:
fresh rhubarb, chopped
granulated sugar
cornstarch
vanilla extract
lemon juice
water

directions

1. I preheat the oven to 350°F and line an 8×8-inch baking dish with parchment paper or lightly grease it.

2. In a large bowl, I mix together the oats, flour, brown sugar, baking soda, and salt.

3. I stir in the melted butter until the mixture is evenly crumbly.

4. I press about two-thirds of the oat mixture into the bottom of the prepared pan to form the crust.

5. In a saucepan over medium heat, I combine the rhubarb, sugar, cornstarch, lemon juice, and water. I cook, stirring often, until the rhubarb softens and the mixture thickens—about 5–7 minutes.

6. I remove it from the heat and stir in the vanilla extract.

7. I pour the filling evenly over the crust, then crumble the remaining oat mixture on top.

8. I bake for 30–35 minutes, or until the topping is golden brown and the filling is bubbling.

9. I let the bars cool completely in the pan before cutting into squares.

Servings and timing

This recipe makes about 9–12 bars and takes around 1 hour—20 minutes of prep, 5–7 minutes for the filling, and 30–35 minutes of baking.

Variations

Sometimes I mix chopped strawberries or raspberries with the rhubarb for a sweeter twist. If I want a nuttier texture, I stir in chopped walnuts or almonds into the oat mixture. I’ve also added a dash of cinnamon to the topping for a warm spice note that pairs beautifully with the fruit.

storage/reheating

I store the bars in an airtight container at room temperature for 2 days or in the fridge for up to 5. They taste great cold or at room temp, and I can warm them slightly in the microwave for a soft, just-baked texture. These bars also freeze well—I wrap them individually and thaw as needed.

FAQs

Can I use frozen rhubarb?

Yes, I can use frozen rhubarb—just thaw it first and drain any excess liquid before making the filling.

Do I need to peel rhubarb before using it?

I don’t usually peel rhubarb unless the stalks are especially thick or tough. Most of the time, a simple rinse and chop is all it needs.

Can I double the recipe?

Yes, I double all the ingredients and bake it in a 9×13-inch pan. I may need to add a few extra minutes to the baking time.

How do I keep the topping crisp?

I bake the bars until the top is nicely golden and cool them uncovered to help retain that crumbly texture.

Are these bars very sweet?

They have a nice balance—just sweet enough to offset the tartness of the rhubarb without being overly sugary. I can adjust the sugar in the filling if I want a sweeter bar.

Conclusion

Rhubarb Oatmeal Bars are a wonderfully simple, tart-sweet treat I love to make when rhubarb is in season. With their buttery crumb topping and fruity filling, they’re a nostalgic dessert that always feels comforting, easygoing, and completely satisfying.