This rhubarb crumble with oats is the perfect balance of sharp, juicy fruit and a golden, buttery topping with just the right amount of crunch. I’ve tested rhubarb crumble a lot over the years, and the biggest mistake people make is overcooking the rhubarb before it goes in the oven — that’s what turns it into mush.
This method gently softens the rhubarb first so it keeps its shape while baking, giving you that perfect contrast between soft fruit and textured crumble topping.
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It’s a proper classic - simple ingredients, minimal prep, and that unmistakable sweet-tart flavour that makes rhubarb crumble so comforting. The addition of oats gives the topping extra texture, making it crisp on top while staying soft and buttery underneath.
Rhubarb crumble has always been more than just a recipe for me. I still remember picking fresh rhubarb in my grandfather’s garden, snapping the stalks straight from the plant and taking them inside to make crumble together.
Years later, I took a cutting from my mum and dad’s rhubarb plant and transplanted it into my own garden. Now, every time I make this rhubarb crumble with oats, it feels like a continuation of that tradition — using something I’ve grown myself and turning it into the same comforting dessert I grew up with.
Ingredients
Please be sure to scroll down to the recipe card for the complete ingredient list and details.
- Rhubarb: The star of the dish - naturally tart and softens beautifully when cooked. Fresh rhubarb works best, but frozen can be used (just thaw and drain first). Cutting into even pieces helps it cook evenly without turning mushy. Bonus points if it comes from your own garden!
For a really quick and easy rhubarb crumble, pick up this tinned stewed rhubarb from M&S and simply make your own crumble topping.
- Caster Sugar: Sweetens the rhubarb and balances its sharpness. You can adjust slightly depending on how tart your rhubarb is (taste once stewed).
Crumble Topping
- Self Raising Flour: Forms the base of the rhubarb crumble topping, giving it structure and a slight lift, while keeping it light. If using plain flour, add 1½ teaspoons of baking powder for the same effect.
- Porridge Oats: Add texture and crunch to the crumble, giving it that slightly rustic finish. Use rolled oats - avoid instant oats as they won’t give the same texture.
- Unsalted Butter: Creates that classic crumbly texture. Keep it cold and rub it into the flour until it resembles breadcrumbs. I wouldn't recommend using salted butter, as I've tested it with that and it's too overpowering and detracts from the taste.
- Golden Granulated Sugar: Adds sweetness and helps the topping caramelise slightly in the oven. You can substitute with light brown sugar for a deeper flavour.
Possible Variations
- Add strawberries for a rhubarb and strawberry crumble
- Swap sugar for brown sugar for a deeper flavour
- Add chopped nuts for extra crunch
How To Make Rhubarb Crumble with Oats
Preheat oven: Preheat to 180°C fan / 200°C conventional / 350°F.
Prepare the rhubarb: Chop the rhubarb into 1-inch (2.5cm) pieces.
Cook the rhubarb: Add the rhubarb and caster sugar to a large saucepan over medium heat.Cook for 5–10 minutes, stirring occasionally, until slightly softened. Don’t overcook — the rhubarb should hold its shape.
Make crumble topping: Rub the flour and butter together until the mixture resembles breadcrumbs (a few small lumps are fine). Stir through the oats and golden sugar until evenly combined.
Assemble + Bake: Transfer the rhubarb to an ovenproof dish, then evenly scatter over the crumble topping. Sprinkle a little extra sugar on top for added crunch. Bake for 30 minutes, or until the topping is golden and the fruit is bubbling around the edges.
Top Tips for Rhubarb Crumble with Oats
- Don’t Overcook the Rhubarb: Lightly soften it before baking, but stop while it still holds its shape — this prevents a mushy filling.
- Keep the Butter Cold: Cold butter creates a better crumble texture. Warm butter will make the topping dense rather than crumbly.
- Use Rolled Oats for Texture: These give the crumble a crisp, slightly chewy finish. Avoid instant oats as they soften too much.
- Don’t Pack the Topping Down: Keep it light and crumbly when adding it on top — this helps it bake evenly and stay crisp.
- Bake Until Bubbling: The filling should be visibly bubbling at the edges — this ensures the fruit is fully cooked and the sugars have caramelised.
Serving Suggestions
Best served warm with:
- Custard (classic) - seen below
- Vanilla ice cream
- Double cream
FAQs
Yes - just thaw and drain off excess liquid before cooking.
Use cold butter, don’t overmix the topping, and bake until golden. Reheating in the oven rather than the microwave also helps maintain the crunch.
Yes - assemble and refrigerate, then bake fresh.
Yes - freeze before or after baking and reheat thoroughly once defrosted.
Caster sugar works well for the rhubarb, while golden granulated or light brown sugar adds a deeper flavour and slight caramelisation to the crumble topping.
You can slightly reduce the sugar, but keep in mind rhubarb is naturally very tart. Reducing too much may make the crumble overly sharp.
Other British Bakes You'll Love!
This rhubarb is everything you want from a classic British dessert. It’s the kind of recipe that never goes out of style, and once you’ve made it, you’ll see just how easy it is to recreate that proper home-style fruit crumble at home. Other classic desserts you could try include:
If you have any questions, please leave a comment, and I'll get back to you. Or I would really appreciate it if you left me a review below.
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Rhubarb Crumble with Oats
Ingredients
Rhubarb Base
- 900 g rhubarb
- 150 g caster sugar
Crumble Topping
- 175 g self raising flour or plain flour with 1.5 teaspoon baking powder
- 30 g porridge oats
- 150 g unsalted butter
- 120 g golden granulated sugar + extra to sprinkle on top
Instructions
- Preheat your oven to 180°C (fan) / 200C / 400F / Gas Mark 6
- Chop 900 g rhubarb into inch (2.5cm) long pieces
- In a large saucepan over medium heat, add the chopped rhubarb and 150 g caster sugar
- Cook until the fruit is slightly softened, stirring occasionally throughout (don’t overcook as the rhubarb will lose its shape and integrity and you’ll end up with mush - it should take approx 5-10 minutes)
- Crumb together 175 g self raising flour (+baking powder if using plain flour) and 150 g unsalted butter (cut into cubes) until resembles breadcrumbs (don’t worry too much if there are still small lumps of butter)
- Mix through 30 g porridge oats and 120 g golden granulated sugar until combined
- Add cooked rhubarb into an oven proof dish and top with the crumble mixture
- Sprinkle some extra sugar on top then bake in the oven for 30 minutes until golden and bubbling
Notes
- Don’t Overcook the Rhubarb: Lightly soften it before baking, but stop while it still holds its shape — this prevents a mushy filling.
- Keep the Butter Cold: Cold butter creates a better crumble texture. Warm butter will make the topping dense rather than crumbly.
- Use Rolled Oats for Texture: These give the crumble a crisp, slightly chewy finish. Avoid instant oats as they soften too much.
- Don’t Pack the Topping Down: Keep it light and crumbly when adding it on top — this helps it bake evenly and stay crisp.
- Bake Until Bubbling: The filling should be visibly bubbling at the edges — this ensures the fruit is fully cooked and the sugars have caramelised.
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