Sweet and Tart Rhubarb Oat Bars That Taste Like Summer

There’s something truly special about the tangy, fresh taste of rhubarb when it’s paired with a buttery oat crumble. These Rhubarb Oat Bars are the ultimate spring and summer dessert bar—bursting with juicy rhubarb flavor and balanced by a sweet, golden oat crust that’s both hearty and tender. Whether you’re using rhubarb fresh from the garden or from your local market, this recipe turns those vibrant stalks into a rustic, crowd-pleasing treat that’s perfect for picnics, brunches, potlucks, or an afternoon snack with coffee.

One of the best things about these rhubarb oat bars is how simple they are to make. You don’t need a mixer or fancy equipment, and you probably already have most of the ingredients in your pantry. They’re made with a combination of flour, oats, butter, and sugar for the crust and crumble topping, while the filling is all about the rhubarb—with a bit of sweetness to offset its natural tartness. The result is a dessert that’s perfectly layered, richly textured, and irresistibly delicious.

What Are Rhubarb Oat Bars and Why They’re So Popular

Rhubarb Oat Bars are classic dessert bars made by sandwiching a tangy rhubarb filling between two layers of oat-based crust and crumble. The bottom layer is pressed firmly into a baking dish to form a sturdy base, while the top layer is sprinkled on for a crispy, golden topping. The rhubarb, either stewed slightly or tossed with sugar and cornstarch, softens beautifully during baking and becomes almost jammy in texture—just thick enough to hold its shape but still melt-in-your-mouth delicious.

They’ve become incredibly popular for a few key reasons. First, they’re a fantastic way to use rhubarb, which is often underutilized outside of pies. Second, the combination of oats and rhubarb creates a perfect flavor balance—earthy and nutty from the oats, sharp and fruity from the rhubarb. Finally, they store well, freeze well, and can be made ahead of time, making them a practical choice for both bakers and busy hosts.

Why You’ll Love These Rhubarb Crumble-Style Bars

These bars are beloved by bakers for many reasons, and once you try them, you’ll understand why. First, the prep is straightforward and forgiving. Even if your measurements aren’t perfect or your rhubarb is a little more tart than expected, the final result is always delightful. Second, the bars strike a unique balance of rustic charm and impressive flavor. You can dress them up for a gathering or keep them casual for a weeknight dessert.

They’re also naturally easy to make in large batches, and they cut cleanly once cooled, making them perfect for parties or gifting. Not to mention, the oats and fruit combo makes them feel just healthy enough to enjoy for breakfast—especially if paired with a scoop of yogurt.

Save

Ingredients You’ll Need to Make Rhubarb Oat Bars

Here’s what you’ll need for this irresistible recipe:

For the crust and topping:

• 1 cup all-purpose flour
• 1 cup old-fashioned rolled oats
• ¾ cup brown sugar, packed
• ½ teaspoon baking soda
• ¼ teaspoon salt
• ½ cup butter, melted

For the rhubarb filling:

• 2½ cups fresh or frozen chopped rhubarb (½-inch pieces)
• ½ cup granulated sugar
• 1 tablespoon cornstarch
• 1 teaspoon vanilla extract
• Optional: 1 tablespoon lemon juice (to brighten the filling)

This ingredient list is beautifully simple. The crust and topping use the same base, which not only streamlines the process but also ensures every bite has that buttery, crumbly goodness. The filling is minimal to let the rhubarb shine, and the cornstarch thickens it just enough to hold together.

Essential Baking Tools for Easy Rhubarb Bars

You won’t need any specialized tools to make these bars. A few basic kitchen items will get the job done with ease:

• 8×8 or 9×9-inch square baking dish
• Mixing bowls (one for the crust/topping, one for the filling)
• Measuring cups and spoons
• Whisk or fork
• Spatula or wooden spoon
• Parchment paper (optional, for easy removal)

If you’re doubling the recipe, use a 9×13-inch pan and increase baking time slightly. Parchment paper is helpful if you plan to lift and cut the bars neatly for serving.

Step-by-Step Instructions to Make Rhubarb Oat Bars

1. Preheat the Oven and Prepare the Pan
   Preheat your oven to 350°F (175°C). Lightly grease your baking dish or line it with parchment paper, leaving some overhang for easier removal later.
2. Make the Crust and Crumble Topping
   In a mixing bowl, combine flour, oats, brown sugar, baking soda, and salt. Stir until everything is evenly mixed. Add the melted butter and mix until crumbly. Reserve about ¾ cup of this mixture for the topping, and press the remaining into the bottom of the prepared pan to form a firm crust.
3. Prepare the Rhubarb Filling
   In another bowl, toss the chopped rhubarb with sugar, cornstarch, vanilla, and lemon juice if using. Stir until the rhubarb is well coated and the sugar starts to dissolve.
4. Assemble the Bars
   Spread the rhubarb mixture evenly over the prepared crust. Sprinkle the reserved oat crumble mixture over the top, pressing down gently to help it adhere.
5. Bake Until Golden and Bubbling
   Bake the bars for 35–40 minutes, or until the top is golden brown and the rhubarb is bubbling slightly at the edges. The filling will continue to set as the bars cool, so don’t worry if it looks a little soft straight out of the oven.
6. Cool and Slice
   Let the bars cool completely in the pan before slicing. For the cleanest cuts, refrigerate them for about 30 minutes before serving.

Tips for a Perfect Crumbly Oat Crust and Tangy Rhubarb Filling

For the crust and topping, using melted butter ensures the oat mixture comes together easily without a food processor. Just be sure to press the bottom layer firmly so it holds together when sliced. As for the rhubarb, use fresh if available, but frozen works great too—just don’t thaw it before baking, or you risk a soggy crust.

Balancing sweetness is key. If your rhubarb is very tart, feel free to add an extra tablespoon of sugar. On the other hand, if you love tart desserts, reduce the sugar slightly and enjoy that bold rhubarb punch.

Serving Ideas: How to Enjoy Rhubarb Oat Bars

These bars are incredibly versatile when it comes to serving. You can plate them simply as a snack or add a dollop of whipped cream or scoop of vanilla ice cream to make them a full dessert. They’re also delicious with Greek yogurt for breakfast, or as part of a brunch board with fresh fruit, muffins, and coffee.

For entertaining, cut the bars into smaller bites and arrange them on a dessert tray with lemon bars, brownies, and shortbread cookies for a beautiful variety. Their natural pink hue from the rhubarb makes them stand out beautifully on any spread.

Save

Fun Add-Ins and Variations You Can Try

Want to put a twist on the classic Rhubarb Oat Bars? Here are a few fun ways to change things up:

• Add ½ cup sliced strawberries for a strawberry-rhubarb variation
• Mix in a few tablespoons of chopped crystallized ginger for warmth
• Replace some oats with coconut flakes for a tropical hint
• Use a drizzle of white chocolate on top for a fancier finish
• Add chopped pecans or walnuts to the topping for crunch and richness

These simple additions allow you to customize the bars based on what you have on hand or the occasion you’re baking for.

How to Store and Freeze Rhubarb Oat Bars

Once cooled, store the bars in an airtight container at room temperature for up to 2 days, or refrigerate for up to 5 days. For longer storage, these bars freeze beautifully. Place them in a single layer on a baking sheet to freeze, then transfer to a container or zip-top bag. They’ll keep well for up to 2 months.

To serve from frozen, simply thaw at room temperature or warm slightly in the microwave for a soft, fresh-out-of-the-oven feel.

Common Mistakes to Avoid When Baking Rhubarb Bars

Avoid over-baking, which can dry out the oat topping and make the rhubarb filling too sticky. Also, make sure not to use too much sugar—while rhubarb is tart, too much sweetener can overwhelm its natural flavor. Finally, resist the urge to slice while warm; give the bars time to cool and set, or they may fall apart.

Rhubarb Oat Bars FAQs

Can I make these gluten-free?
Yes! Use a gluten-free all-purpose flour and certified gluten-free oats.

Do I need to peel rhubarb?
No, just trim the ends and slice. The skin softens nicely during baking.

Can I double the recipe?
Absolutely. Use a 9×13-inch pan and increase the bake time by about 5–10 minutes.

Can I make these vegan?
Yes. Substitute the butter with coconut oil or a vegan butter alternative.

What’s the best way to cut them cleanly?
Chill the bars for 30 minutes after cooling, then use a sharp knife wiped clean between cuts.

Conclusion

These Rhubarb Oat Bars are a sweet, tart, and buttery dessert that celebrates everything we love about seasonal baking. With their golden crumbly crust and vibrant rhubarb filling, they offer the perfect balance of rustic charm and satisfying flavor. Whether you’re enjoying them with your morning coffee, bringing them to a picnic, or serving them for dessert with ice cream, these bars are sure to become a favorite in your recipe collection.

If you loved this recipe, don’t forget to share it with your friends and family and subscribe to our blog for more cozy, fruit-filled baking ideas all year long.

Print