Craving that golden, bubbly, tart-sweet dessert but fresh rhubarb is nowhere in sight? Good news: this traditional rhubarb crisp with frozen rhubarb is every bit as delicious as the real thing — maybe even easier.
I first made this on a random Tuesday in January when I spotted a forgotten bag of rhubarb in the back of my freezer. One crisp later, I was fully obsessed. No regrets, only crumbles.
Table of Contents
Why You’ll Love This Rhubarb Crisp
This recipe is your go-to when the rhubarb season is long gone but the craving hits hard. Frozen rhubarb works beautifully here — no thawing drama, no watery mess when you handle it right.
The filling is perfectly tart and jammy, balanced by a buttery oat topping that goes shatteringly crisp in the oven. Think cozy farmhouse dessert vibes, ready in under an hour.
It’s also wildly flexible. You can turn it into a strawberry rhubarb crisp with frozen rhubarb by swapping half the rhubarb for frozen strawberries. More on that below!
Traditional Rhubarb Crisp With Frozen Rhubarb
Equipment
- 2-quart casserole dish
- Mixing bowl
- pastry cutter or forks
- Oven
Ingredients
The Filling
- 2 lb frozen rhubarb cut into 1-inch pieces, kept frozen
- ¾ cup granulated sugar adjust to taste
- ¼ cup cornstarch for thickening
- ½ tsp cinnamon
The Crisp Topping
- 1 cup old-fashioned rolled oats do not use instant
- ½ cup all-purpose flour
- ½ cup granulated sugar
- ½ tsp cinnamon
- ½ cup unsalted butter cold, cut into cubes
- 1 pinch salt
Instructions
- Preheat oven to 400°F (200°C) and lightly butter a 2-quart casserole dish.
- In a large bowl, mix frozen rhubarb, sugar, cornstarch, and cinnamon until evenly coated. Spread into the prepared dish.
- In another bowl, combine oats, flour, sugar, cinnamon, and salt. Cut in cold butter using a pastry cutter or fingers until crumbly.
- Sprinkle the crumble topping evenly over the rhubarb mixture without pressing it down.
- Bake for about 35 minutes until the topping is golden and the filling is bubbling. Let cool for 10 minutes before serving.
Notes
Ingredients You’ll Need
Here’s everything laid out cleanly so you can grab it all before you start. Nothing fancy — just good, honest pantry staples.
The Filling
| Ingredient | Amount | Notes |
|---|---|---|
| Frozen rhubarb | 2 lb | Cut into 1-inch pieces, kept frozen |
| Granulated sugar | 3/4 cup | Adjust to taste if rhubarb is very tart |
| Cornstarch | 1/4 cup | Thickens the juicy filling |
| Cinnamon | 1/2 tsp | Adds warm spice to the fruit |
The Crisp Topping
| Ingredient | Amount | Notes |
|---|---|---|
| Old-fashioned rolled oats | 1 cup | Best texture — do not use instant oats |
| All-purpose flour | 1/2 cup | Holds the crumble together |
| Granulated sugar | 1/2 cup | Sweetens and helps it crisp up |
| Cinnamon | 1/2 tsp | Echoes the spice in the filling |
| Cold unsalted butter | 1 stick (1/2 cup) | Cut into small cubes — cold is key! |
| Salt | 1 pinch | Balances the sweetness |
Love the idea of using oats in healthy ways? Check out these healthy overnight oats recipes for more oat-based inspiration beyond dessert.
How to Make Traditional Rhubarb Crisp With Frozen Rhubarb
No complicated techniques here. Just five easy steps and about 45 minutes of your time (most of which is hands-off oven time — my favorite kind of cooking).
Step 1: Preheat and Prep Your Dish
Preheat your oven to 400°F (200°C). While it’s heating up, lightly butter a 2-quart casserole dish. This stops the filling from gluing itself to the bottom — trust me, you’ll thank yourself at the washing-up stage.
Step 2: Mix the Rhubarb Filling
Grab a large bowl and toss in your frozen rhubarb, sugar, cornstarch, and cinnamon. Mix it all together until the rhubarb is well coated in that sugary, spiced mixture.
Don’t thaw the rhubarb beforehand! Using it straight from frozen helps it hold its shape and prevents the filling from turning into a watery soup.
Spread the mixture evenly into your buttered casserole dish. You’ll hear that satisfying thud of frozen fruit hitting the pan — good sign you’re on the right track.
Step 3: Make the Crumble Topping
In a second large bowl, combine the oats, flour, sugar, cinnamon, and salt. Give it a quick stir to distribute everything evenly.
Now add the cold butter cubes. Use a pastry cutter, two forks, or honestly just your fingertips to work the butter into the dry ingredients. You’re aiming for a rough, crumbly texture — like wet sand but better.
Pro tip: Cold butter is non-negotiable here. Warm butter will make your topping greasy instead of crispy. If your kitchen is warm, pop the butter back in the fridge for 5 minutes before using.
If you love a rhubarb crisp without oatmeal, you can skip the oats and just double the flour for a classic shortbread-style crumble. Still delicious, just a different texture.
Step 4: Assemble and Bake
Scatter the crumble topping evenly over the rhubarb filling. Don’t pack it down — a loose, uneven layer bakes up with more crunchy nooks and crannies.
Slide the dish into your preheated oven and bake for about 35 minutes. You’ll know it’s ready when the topping is deep golden and the rhubarb filling is bubbling up around the edges.
That bubbling is key! It means the cornstarch has activated and your filling will be thick and glossy, not runny.
Step 5: Cool Slightly and Serve
Pull the crisp from the oven and let it rest for at least 10 minutes. I know it’s hard to wait — the smell alone is agony. But this rest time lets the filling thicken up beautifully.
Serve it warm with a generous scoop of vanilla ice cream or a dollop of whipped cream. That cold-meets-warm, crunchy-meets-jammy contrast? Absolutely perfect.
Expert Tips, Variations, and Troubleshooting
Getting the Best Results
Always use old-fashioned rolled oats, not quick oats or instant. Quick oats go mushy in the oven and you lose that satisfying crunch that makes a crisp a crisp.
If your frozen rhubarb pieces are huge, break them up a bit before tossing with the filling ingredients. More surface area means more even cooking and better flavor distribution.
Fun Variations to Try
Want to make a strawberry rhubarb crisp with frozen rhubarb? Just swap 1 lb of rhubarb for 1 lb of frozen strawberries. The strawberries add natural sweetness so you can reduce the sugar slightly too.
Feeling adventurous? Turn this into a berry rhubarb crumble by using a mix of frozen blueberries, raspberries, and rhubarb. The combination is gorgeous and deeply purple — and it tastes even better than it looks.
You can also add a handful of chopped walnuts or pecans to the topping for extra crunch and a nutty richness. Highly recommended if you’re a texture person.
Love rhubarb in other forms? You’ll also adore this moist and tender rhubarb cake — it’s another crowd-pleaser that uses rhubarb in the most delicious way.
Troubleshooting Common Issues
Topping not getting crispy? Your oven might be running cool, or the topping layer was too thin. Bake for an extra 5-8 minutes, checking every few minutes so it doesn’t burn.
Filling too watery? This usually happens if the rhubarb was thawed before using. Next time, keep it frozen. If it happens, just bake for an additional 10 minutes — the cornstarch will eventually thicken things up.
Topping burning before filling bubbles? Loosely tent the dish with foil halfway through baking. This protects the topping while the filling catches up.
Storage Instructions
This crisp stores really well, making it a great make-ahead dessert for gatherings or weeknight treats.
| Storage Method | How Long | Best Practice |
|---|---|---|
| Room temperature | Up to 2 days | Cover loosely with foil or a clean towel |
| Refrigerator | Up to 5 days | Cover tightly with wrap or airtight lid |
| Freezer | Up to 3 months | Wrap well in foil, then a freezer bag |
Reheating Tips
To reheat, pop individual portions in a 350°F oven for about 10-15 minutes. This revives the crunch in the topping in a way the microwave simply cannot. If you’re in a hurry, the microwave works fine — just expect a softer topping.
No-Waste Kitchen Ideas
Got leftover crisp that’s gone a bit soggy? Crumble it over yogurt or oatmeal the next morning for a dessert-for-breakfast situation that nobody will judge you for.
Extra crumble topping? Freeze it in a zip-lock bag. It keeps for up to 3 months and you can sprinkle it straight from frozen onto fruit anytime a craving strikes. Speaking of no-waste oat ideas, this article about the Dr. Neal Barnard oat trick has some genuinely interesting ideas for making oats work harder in your kitchen.
Traditional Rhubarb Crisp With Frozen Rhubarb FAQs
Can I use frozen rhubarb without thawing it first?
Yes, and in fact you should! Using frozen rhubarb straight from the freezer helps it hold its shape and prevents the filling from becoming watery. Thawed rhubarb releases a lot of liquid, which can make the crisp soggy. Keep it frozen until the moment you mix it with the filling ingredients.
Can I make this rhubarb crisp without oatmeal in the topping?
Absolutely. If you prefer a rhubarb crisp without oatmeal, just replace the oats with an equal amount of flour for a total of 1 1/2 cups flour. The result is a denser, more shortbread-like crumble — still delicious, just a different texture experience.
How do I know when the rhubarb crisp is done baking?
Look for two things: a deep golden-brown topping and filling that’s visibly bubbling around the edges of the dish. The bubbling is especially important — it signals that the cornstarch has thickened the filling properly. If only the topping looks done but the filling isn’t bubbling, give it another 5-10 minutes.
Can I turn this into a strawberry rhubarb crisp with frozen rhubarb?
Yes! Replace 1 lb of the frozen rhubarb with 1 lb of frozen strawberries. Since strawberries are sweeter, reduce the sugar in the filling to about 1/2 cup. Everything else stays the same. The result is a gorgeous, rosy-pink filling that’s less tart and beautifully balanced.
What can I serve with this rhubarb crisp?
Vanilla ice cream is the classic and honestly unbeatable pairing — the cold creaminess against the warm, bubbly crisp is just magic. Whipped cream or a dollop of thick Greek yogurt also work beautifully. If you want to keep it lighter, even a drizzle of cold cream does the job.
More Rhubarb Recipes to Love
Once you’re in a rhubarb mood, it’s hard to stop. This rhubarb cinnamon jam recipe is a wonderful way to preserve that tart, spicy flavor — perfect on toast, scones, or spooned over yogurt.
And if you’re looking for something completely different to round out your recipe browsing, this Japanese egg salad sandwich is a surprisingly addictive lunch idea you won’t regret trying.
Time to Bake This Beauty
This traditional rhubarb crisp with frozen rhubarb is the kind of recipe that makes your whole kitchen smell incredible and earns serious compliments with minimal effort. Tart, sweet, golden, and gloriously crunchy — it’s a classic for a reason.
Whether you stick with pure rhubarb, go for a strawberry rhubarb crisp with frozen rhubarb, or jazz things up as a berry rhubarb crumble, you really cannot go wrong here.
Give it a try this week and let me know how it goes! Drop your thoughts, tweaks, and triumphs in the comments below. And if you loved it, please share it on Pinterest — your followers deserve to know about this one.
