Irresistible Rhubarb Crumble Bars with Oat Topping in 35 Minutes

Name: Irresistible Rhubarb Crumble Bars with Oat Topping in 35 Minutes
Prep time: 15 min
Cook time: 35 min
Total time: 50 min
Cuisine: American
Ingredients: 2 cups chopped rhubarb; 1/2 cup granulated sugar; 1 tbsp cornstarch; 1 cup all-purpose flour; 1 cup rolled oats; 1/2 cup brown sugar; 1/2 tsp cinnamon; 1/2 cup melted butter

Author: Carry

Published: February 17, 2026

Jump to Recipe

Oh, rhubarb – that tart, pink stalk that makes my taste buds dance! I remember sneaking into Grandma’s garden as a kid, snapping off a stalk of rhubarb and immediately puckering from its sour bite. Who knew that same mouth-puckering veggie (yes, it’s technically a vegetable!) could transform into the star of these incredible rhubarb crumble bars with oat topping? The magic happens when you pair tangy rhubarb with a sweet, buttery oat crumble that bakes up crisp and golden. What I love most? These bars come together in about the time it takes to preheat your oven – no fancy techniques, just simple ingredients becoming something extraordinary. One bite of that jammy rhubarb layer sandwiched between the crunchy oat topping, and you’ll understand why this recipe never lasts more than a day in my house!

Why You’ll Love These Rhubarb Crumble Bars with Oat Topping

Trust me, these bars are about to become your new favorite dessert. Here’s why:

Easy as pie (but way simpler): No fancy equipment needed – just mix, layer, and bake. Perfect for when you need a quick dessert that looks like you spent hours!
That killer sweet-tart combo: The tangy rhubarb filling plays perfectly against the sweet, buttery oat topping – it’s a match made in dessert heaven.
Crunch you can hear: That golden oat topping stays crisp for days, giving every bite the most satisfying texture.
Always a crowd-pleaser: Whether it’s a potluck or just Tuesday night, these bars disappear fast. I always make a double batch!

rhubarb crumble bars with oat topping - detail 1

Ingredients for Rhubarb Crumble Bars with Oat Topping

Here’s everything you’ll need for these addictive bars (and yes, I’ve learned the hard way – measure carefully!):

2 cups chopped rhubarb – about 4 medium stalks, trimmed and cut into ½-inch pieces (don’t use the leaves – they’re poisonous!)
½ cup granulated sugar – this tames the rhubarb’s tartness just right
1 tablespoon cornstarch – our secret weapon for thickening that juicy filling
1 cup all-purpose flour – spooned and leveled, please!
1 cup old-fashioned rolled oats – not instant oats, or your topping won’t have that perfect crunch
½ cup packed brown sugar – press it firmly into your measuring cup
½ teaspoon cinnamon – just enough warmth without overpowering the rhubarb
½ cup melted butter – I use unsalted, but if you only have salted, just skip adding extra salt

How to Make Rhubarb Crumble Bars with Oat Topping

Okay, let’s get baking! These rhubarb crumble bars come together in three simple steps – filling, topping, and assembly. I promise, even if you’re not a confident baker, you can’t mess this up. Just follow my lead!

Preparing the Rhubarb Filling

First, toss your chopped rhubarb with granulated sugar and cornstarch in a medium bowl. Don’t be shy – get in there with your hands and mix it well! The sugar will start pulling out the rhubarb’s juices almost immediately. Let this sit while you make the topping – about 10 minutes is perfect. You’ll see the mixture get nice and syrupy. That’s exactly what we want!

Making the Oat Crumble Topping

Now, grab a big bowl and whisk together the flour, oats, brown sugar, and cinnamon. Pour in the melted butter and use a fork to mix until you’ve got a crumbly, sandy texture with some larger clumps. Pro tip: If the mixture seems too dry, add another tablespoon of melted butter. You want it to hold together when squeezed but still break apart easily.

Assembling and Baking the Bars

Here’s where the magic happens! Press half of your oat mixture firmly into a greased 8×8 inch baking dish (I use my fingers – it’s messy but effective). Spread the rhubarb filling evenly over the base, then sprinkle the remaining oat topping over everything. Don’t press this layer down – we want those beautiful peaks to get nice and crisp! Bake at 350°F for 35-40 minutes until the filling is bubbling around the edges and the topping is golden brown. This part kills me – you MUST let it cool completely before cutting, about 1-2 hours. I know it smells amazing, but trust me, waiting means perfect, clean slices!

Tips for Perfect Rhubarb Crumble Bars with Oat Topping

After making these bars more times than I can count, here are my foolproof tips for rhubarb crumble perfection:

Fresh is best: Seek out firm, bright pink rhubarb stalks – they have the best flavor and texture for baking.
Patience pays off: Letting the bars cool completely (I know, it’s hard!) means clean cuts and set filling.
Watch for bubbles: When the edges are golden and you see thick bubbles in the filling, they’re done – don’t overbake!
Press that base: Really pack down the first oat layer so it holds together when you slice the bars.

Variations for Rhubarb Crumble Bars with Oat Topping

Oh, the possibilities! While I adore the classic version, sometimes I like to mix things up:

Berry buddies: Swap half the rhubarb for strawberries or raspberries – their sweetness balances the rhubarb’s tang beautifully.
Spice it up: Try ground ginger or cardamom instead of cinnamon for a warm, exotic twist.
Nutty crunch: Toss a handful of chopped pecans or almonds into the oat topping for extra texture.
Citrus zing: Grate some orange zest into the rhubarb filling – it brightens everything up!

Serving and Storing Rhubarb Crumble Bars with Oat Topping

Oh, the ways to enjoy these beauties! I love them slightly warm with a scoop of vanilla ice cream melting over that crisp oat topping – pure heaven. But they’re just as good at room temperature with your afternoon tea. For storage, pop them in an airtight container at room temperature for up to 3 days (if they last that long!). The oat topping stays surprisingly crisp! You can also freeze them for up to a month – just layer between parchment paper so they don’t stick together. A quick 10-second zap in the microwave brings them right back to life.

Nutritional Information for Rhubarb Crumble Bars with Oat Topping

Here’s the scoop on what’s in these delicious bars (per serving, based on cutting into 12 pieces):

180 calories – perfect little treat-sized portions!
7g fat (4g saturated) – thank you, butter, for making life delicious
28g carbs with 2g fiber – those oats are working for you
14g sugar – mostly from the natural rhubarb sweetness

Remember, these numbers can vary based on your exact ingredients – like if you use more rhubarb or different sugar amounts. But honestly? When something tastes this good, I try not to think too hard about the numbers!

Frequently Asked Questions About Rhubarb Crumble Bars with Oat Topping

I get asked about these bars all the time – here are the answers to the questions that pop up most often:

Can I use frozen rhubarb? Absolutely! Just thaw and drain it well – I’ll even pat it dry with paper towels so the filling doesn’t get too watery. You might need an extra teaspoon of cornstarch.

Can I make these gluten-free? You bet! Swap the all-purpose flour for your favorite gluten-free blend (I like the 1:1 kinds). The texture comes out nearly identical!

How long do they keep? About 3 days at room temperature in an airtight container – if you can resist eating them all sooner! They freeze beautifully for up to a month too.

Can I double the recipe? Please do! Just use a 9×13 pan instead and add 5-10 minutes to the baking time. I always double it – these disappear fast!

Why is my topping not crispy? Usually means you packed it down too much or didn’t bake long enough. Next time, sprinkle it loosely and wait for those golden edges!