Easy Blueberry & Rhubarb Crisp with Oats Crumble Topping

This is easy to make blueberry and rhubarb crisp with oats crumble topping baked in the oven to perfection. A hint of cinnamon and lemon brings all the flavours together and makes this a great comfort food. Great for pudding, an afternoon snack or even a lazy breakfast!

I love porridge oats, so when I came across a recipe for a traditional apple crisp I got really excited that the recipe topping included oats.

I've previous made fruit crumble, but the UK version doesn't usually includes oats, just flour, butter and sugar.

This recipe is much more substantial, the oats pretty much make it into a stand-alone meal. Breakfast anyone?

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Why I really like this recipe

• Super easy to make (and the whole house smells amazing when it's baking)
• Great flavour combination, which I often change around and add different spice or fruit
• Lower the sugar content if you prefer

Blueberry & Rhubarb crisp ingredients + substitutions you can use

Rhubarb

Use fresh or frozen rhubarb cut up into 1 cm chunks. Like with my Rhubarb & Yoghurt Cake recipe, there is no need to pre-cook the rhubarb, it will be cooked/baked together with the blueberries.

Blueberries

I've used fresh blueberries, but you are welcome to use frozen ones too. If you use frozen fruit in the filling, the crisp should be eaten with 1-2 days and not frozen again.

If you use fresh fruit, you can freeze the crisp, but the topping might be slightly soggy when you defrost it. You can easily crisp up the top by putting to the oven for 10 min on 180C to warm up.

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Sugar

I've used basic granulated white sugar with this recipe, but you can substitute it for brown sugar or other types of sugar like a coconut sugar, which works with this recipe really well.

You do need the crunch in the sugar and the melting element, which means that substituting normal sugar for man-made sugars like Splenda doesn't work as well.

If you are worried that this recipe has too much sugar, reduce the amount by a bit. It will still taste amazing.

Oats

The best oats for this recipe are traditional breakfast oats, large steel-cut or Scottish Oats.

Unless you have absolutely no other options, don't use instant oats as they will lose their texture and will turn into a sort of mush.

Flour

I've used plain (all purpose flour), but you are welcome to use any other low gluten - plain - flour. If you fancy a wholemeal version of this recipe, you can try wholemeal plain flour, spelt or buckwheat flours.

If you are after a gluten free fruit crisp, you are welcome to use any gluten plain (all purpose flour).

There is no need to use xanthan gum with the flour as it's only used for topping and we don't need to worry about the flour keeping a particular structure (like if you are baking a cake).

You will find that some recipes use flour in the filling too. This is so that the filling is not too soggy. If you want to do that, 1-2 tablespoons of plain flour are enough to thicken the filling.

You can also use cornflour (or corn-starch). I prefer to keep my fruit as it is and just add less water.

Lemon

Rhubarb and blueberries have a lovely flavour, but they can be improved with a dash of lemon as it adds sharpness to the dish. With the sweet crisp topping, it's the perfect combination.

Mixed Spice

I like to add some spice to my fruit crisps, whether it's cinnamon or mixed spice. It just adds extra warmth to the recipe and it makes it into a super comforting food.

Butter

I've used unsalted butter, which is melted and added to create the crumble topping at room temperature.

To achieve that crumbly, yet crisp texture on the top of your filling, it's best to use melted butter that soaks up the flour and oats and doesn't run down into the filling when it starts to get hot in the oven.

It makes perfect sense when you think about it, but if you add the butter cold and create a crumble, you will very likely end up with most of the butter in the rhubarb and a dry crisp topping.

If you don't have unsalted butter, you can also use salted butter but then don't add any more salt to your crisp topping.

If you don't have any butter at all, you can also use butter substitutions, such as coconut oil or margarine, but the flavour of your crisp topping will change.

How to make Blueberry & Rhubarb Crisp recipe

To make the topping, mix together the flour, oats, a pinch of salt and sugar.

Add the melted butter and work it into the flour mixture to create a crumble.

In another bowl mix together the rhubarb, blueberries, lemon juice, lemon grind, mixed spice (or cinnamon) and water.

Scoop the filling into the baking dish

Sprinkle topping over the filling mixture evenly and pat down gently.

Bake at 180C (Gas mark 3) 350°F for 30 minutes until the top is golden brown and the rhubarb is soft.

What to serve the Blueberry & Rhubarb Crisp with

Serve warm (or hot) as it is or with my traditional homemade vanilla ice cream, it's the perfect combination. Whipped cream is another great option; it adds this light, airy sweetness that balances out the tart rhubarb.

If you're in the mood for something richer, custard is amazing with it. For a healthier twist, a dollop of Greek yogurt works really well too. And if you want to keep it simple, just pour a bit of fresh cream over the top. Trust me, any of these will take your dessert to the next level!

How to store homemade crisp

To store homemade crisp and keep it fresh, make sure it is completely cool before storing. Place the crisp in an airtight container to prevent moisture from getting in, which can make it soggy.

You can also use a resealable plastic bag, ensuring to squeeze out as much air as possible before sealing it tightly. If you find the crisp a bit greasy, you can place a paper towel at the bottom of the container or bag to absorb any excess oil. Stored this way, your homemade crisp should stay fresh and crispy for up to a week.

How long can you keep freshly baked fruit based crips for?

Freshly baked fruit-based crisps can be stored in the refrigerator for up to 5 days. To ensure they stay fresh, cover the crisp with foil or plastic wrap, or store it in an airtight container. If you want to keep it for a longer period, you can freeze the crisp for up to 3 months. When ready to enjoy, thaw it in the refrigerator and reheat it before serving.

This recipe blog post was originally written on 1 September 2020 and last tested and updated on 14 January 2025