Oat Rhubarb Crumble with Lemon Drizzle

Published: June 6, 2026

Oat Rhubarb Crumble with Lemon Drizzle is a warm, comforting dessert with soft tart rhubarb underneath a golden oat topping and a bright lemon glaze on top. The crumble bakes into a crisp, buttery layer that pairs beautifully with the juicy fruit filling. It is simple, rustic, and perfect served warm with cream or ice cream.

Ingredients & Substitutions

Rhubarb: Gives the crumble its tart, fruity base. Fresh rhubarb works best, but frozen rhubarb can be used if thawed and drained.
Sugar: Sweetens the rhubarb and balances its sharpness. You can reduce it slightly if your rhubarb is less tart.
Cornstarch: Helps thicken the fruit filling so it does not turn watery.
Lemon juice: Brightens the rhubarb flavor and adds a fresh citrus note.
Oats: Create the hearty, crumbly topping with a rustic texture. Rolled oats are the best choice.
Flour: Helps bind the crumble topping together.
Brown sugar: Adds sweetness and a rich caramel flavor to the topping.
Butter: Makes the crumble rich and crisp. Cold butter gives the best texture.
Cinnamon: Adds a warm spice note that pairs well with rhubarb.
Powdered sugar: Used for the lemon drizzle.
Extra lemon juice: Turns the powdered sugar into a simple glaze that finishes the dessert.

Tips for Success

Cut the rhubarb evenly so it cooks at the same rate.
Use cold butter for the topping to get a crumbly texture instead of a paste.
Do not overmix the crumble; rub it together just until clumpy and coarse.
Bake until bubbling so the fruit filling thickens properly.
Drizzle while warm for a smooth lemon glaze that settles nicely over the crumble.
Let it rest a few minutes before serving so the filling can set slightly.

How to Make Oat Rhubarb Crumble with Lemon Drizzle

Preheat the oven to 180°C.
Mix the rhubarb filling by combining the rhubarb, sugar, cornstarch, and 1 tablespoon lemon juice.
Spread the rhubarb mixture into a baking dish.
Make the crumble topping by combining the oats, flour, brown sugar, cinnamon, and cold butter. Rub the butter in until the mixture becomes crumbly.
Scatter the topping evenly over the rhubarb layer.
Bake for 35 to 40 minutes, until the top is golden and the filling is bubbling.
Make the drizzle by mixing the powdered sugar with 2 tablespoons lemon juice.
Drizzle over the warm crumble and serve warm or at room temperature.

How to Use Oat Rhubarb Crumble with Lemon Drizzle

This crumble is versatile and easy to serve in different ways.

Serve warm with vanilla ice cream.
Add whipped cream for a softer, richer finish.
Spoon it into bowls for a casual family dessert.
Serve it at brunch as a sweet-tart treat.
Enjoy leftovers chilled or reheated the next day.

How to Store Oat Rhubarb Crumble with Lemon Drizzle

Store leftovers in an airtight container in the refrigerator for up to 4 days. The topping will soften slightly, but the flavor stays delicious.

To reheat, warm individual portions in the oven or microwave until just heated through. You can also freeze the baked crumble for up to 2 months and thaw it in the refrigerator before reheating.

FAQs

What does oat rhubarb crumble taste like?

It tastes sweet, tart, buttery, and lightly spiced. The rhubarb gives the dessert brightness, while the oat topping adds a crisp, cozy texture.

Can I use frozen rhubarb?

Yes, frozen rhubarb works well. Thaw it first and drain extra liquid before baking.

Can I make the topping ahead of time?

Yes, the crumble topping can be mixed ahead and kept chilled until needed.

Can I use other fruit with the rhubarb?

Yes, strawberries, apples, or raspberries can be added for a sweeter flavor.

Why is cornstarch used in the filling?

Cornstarch thickens the fruit juices as the crumble bakes, keeping the filling from becoming too runny.

Can I skip the lemon drizzle?

Yes, but the drizzle adds a bright finish that balances the sweetness and tart rhubarb nicely.