Lemon Gluten Free Strawberry Rhubarb Crumble

Here is my favorite gluten-free strawberry rhubarb crumble recipe, with a crispy oat and pecan topping, and a sweet-tart filling bursting with fresh strawberries, tangy rhubarb, and just a hint of lemon and vanilla.

This crumble has become our go-to spring dessert when rhubarb starts showing up at the farmers market. I love that it’s naturally gluten-free but tastes just as good as the traditional version. Serve it warm with a scoop of vanilla ice cream, and watch it disappear!

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What Kind of Rhubarb Should I Use?

Fresh rhubarb is always your best bet for this crumble, and you’ll find it in season during spring and early summer at most grocery stores and farmers markets. The stalks can range from green to deep red, and while the red varieties look prettier, the color doesn’t really affect the taste – both work equally well. Make sure to trim off and discard the leaves since they’re toxic, and only use the stalks for cooking. If you can’t find fresh rhubarb, frozen rhubarb is a solid backup option – just thaw it first and drain any excess liquid before using it in your recipe.

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Options for Substitutions

This crumble is pretty forgiving when it comes to swaps, so here are some options if you need to make changes:

• Rhubarb: If rhubarb isn’t in season or you can’t find it, you can use all strawberries (about 6 cups total) or swap the rhubarb for tart cherries or cranberries. Just taste the filling and adjust the sugar since you’ll lose that tart rhubarb flavor.
• Pecans: Walnuts, almonds, or hazelnuts work great in the topping. You can also leave out the nuts entirely if you have allergies – the crumble will still be tasty.
• Gluten-free oats: Regular old-fashioned oats work fine if you’re not avoiding gluten. Just make sure they’re labeled gluten-free if that’s important to you, as oats can be cross-contaminated during processing.
• Oat flour: You can make your own by grinding gluten-free oats in a food processor until fine. If you’re not gluten-free, regular all-purpose flour works perfectly here.
• Cornstarch: Tapioca starch or arrowroot powder can replace cornstarch in equal amounts for thickening the fruit filling.
• Brown sugar: White sugar mixed with 1 tablespoon of molasses works in a pinch, or you can use coconut sugar for a less refined option.

Watch Out for These Mistakes While Baking

The biggest mistake you can make with fruit crumbles is skipping the maceration step where the strawberries and rhubarb sit with sugar – this draws out excess moisture and prevents a watery filling, so don’t rush it even if you’re short on time.

Another common error is pouring all that fruit juice into the baking dish along with the fruit, which will make your crumble soupy instead of thick and jammy – drain it off and save it for another use.

To get a perfectly golden, crispy topping instead of a pale, soft one, make sure your butter is fully melted and evenly distributed through the oat mixture, and don’t pack the topping down when spreading it over the fruit.

Finally, resist the urge to dig in right away – letting the crumble cool for at least 10 minutes allows the cornstarch to fully thicken the filling so it doesn’t run all over your plate.

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What to Serve With Strawberry Rhubarb Crumble?

This crumble is absolutely perfect with a big scoop of vanilla ice cream on top – the cold, creamy ice cream melting into the warm fruit filling is really something special. If you’re not an ice cream person, try it with a dollop of whipped cream or even some Greek yogurt for a tangy contrast to the sweet fruit. I also love serving this for brunch alongside some strong coffee or tea, since the tartness of the rhubarb pairs nicely with a hot drink. For a fancier presentation, you can drizzle some caramel sauce over the top or add a sprinkle of toasted pecans for extra crunch.

Storage Instructions

Store: Keep any leftover crumble covered with foil or plastic wrap in the fridge for up to 4 days. The topping might lose a bit of its crunch, but it still tastes great. I actually don’t mind eating it cold straight from the fridge for breakfast the next day!

Freeze: You can freeze the baked crumble for up to 3 months in an airtight container. Let it cool completely first, then wrap it well to prevent freezer burn. You can also freeze the unbaked crumble assembled in the baking dish, which is super handy when rhubarb season hits and you want to save some for later.

Warm Up: Reheat individual portions in the microwave for about 30-45 seconds, or warm the whole dish in a 350°F oven for 15-20 minutes until heated through. If you want to crisp up the topping again, pop it under the broiler for a minute or two, keeping a close eye so it doesn’t burn.

Estimated Nutrition

Estimated nutrition for the whole recipe (without optional ingredients):

• Calories: 2100-2300
• Protein: 20-25 g
• Fat: 110-120 g
• Carbohydrates: 290-320 g

Ingredients

For the fruit filling:

• 2 cups rhubarb (sliced into 1/2-inch thick pieces)
• 1 quart strawberries (hulled and halved, or quartered if large)
• 6 tbsp sugar
• 2 tbsp lemon zest
• 3 1/2 tbsp cornstarch (for a reliable thicken)
• 1 tbsp lemon juice
• 1/2 tsp vanilla extract

For the crumble topping:

• 1/2 cup butter (unsalted)
• 1/2 cup pecans (finely chopped into 1/4-inch pieces)
• 1 1/4 cups gluten-free oats
• 3/4 cup brown sugar
• 1/2 cup gluten-free oat flour
• 1/2 tsp salt
• 1/2 tsp ground cinnamon

For the pan and serving:

• 2 tsp butter
• vanilla ice cream (optional but recommended for the temperature contrast)

Step 1: Prepare the Fruit Filling and Extract Juices

• 2 cups rhubarb
• 1 quart strawberries
• 6 tbsp sugar

In separate bowls, toss the sliced rhubarb with 3 tablespoons of sugar and the hulled strawberries with 3 tablespoons of sugar.

Let them sit for 20 minutes to release their natural juices—this maceration step draws out moisture and concentrates the fruit flavor.

After 20 minutes, strain the fruit through a fine-mesh sieve into a bowl, reserving the juices (you should have about 1/2 cup liquid).

Set the drained fruit aside; I discard the excess juice since the cornstarch will provide enough thickening power without making the filling overly wet.

Step 2: Toast Pecans and Prepare Dry Crumble Base

• 1/2 cup pecans
• 1 1/4 cups gluten-free oats
• 3/4 cup brown sugar
• 1/2 cup gluten-free oat flour
• 1/2 tsp salt
• 1/2 tsp ground cinnamon

Preheat your oven to 350°F.

While the oven heats, place the chopped pecans in a small dry skillet over medium heat and toast for 8 minutes, stirring occasionally, until fragrant and lightly golden.

Transfer to a plate and let cool slightly, then finely chop into 1/4-inch pieces if not already done.

In a large bowl, whisk together the gluten-free oats, gluten-free oat flour, brown sugar, salt, and cinnamon.

Set this dry mixture aside—toasting the pecans separately adds a deeper, more complex nutty flavor that’s much better than raw pecans.

Step 3: Build the Fruit Filling with Thickener

• drained fruit from Step 1
• 2 tbsp lemon zest
• 1 tbsp lemon juice
• 1/2 tsp vanilla extract
• 3 1/2 tbsp cornstarch

In a medium bowl, combine the drained fruit from Step 1 with the lemon zest, lemon juice, vanilla extract, and cornstarch.

Stir gently but thoroughly until the cornstarch is evenly distributed throughout the fruit and there are no lumps—this ensures the filling will thicken uniformly as it bakes.

The cornstarch will absorb any remaining moisture from the fruit and set up during baking to create a cohesive but not overly thick filling.

Step 4: Melt Butter and Complete the Crumble Topping

• 1/2 cup butter
• dry crumble mixture from Step 2
• toasted pecans from Step 2

Melt the 1/2 cup unsalted butter in a small saucepan over low heat or in the microwave.

Pour the melted butter into the bowl with the dry crumble mixture from Step 2 and stir until the oat mixture is evenly moistened and clumpy in texture—you want some texture, not a wet paste.

Fold in the toasted pecans from Step 2, distributing them evenly throughout the topping.

Step 5: Assemble and Bake the Crumble

• 2 tsp butter
• fruit filling from Step 3
• crumble topping from Step 4

Lightly grease a 9×13-inch baking dish (or similar size) with the 2 teaspoons of butter.

Spread the fruit filling from Step 3 evenly across the bottom of the prepared pan.

Distribute the crumble topping from Step 4 evenly over the fruit, breaking up any large clumps and leaving it slightly rustic rather than compacted—this allows for better browning and crispier texture.

Bake at 350°F for 25–30 minutes until the filling is bubbling at the edges and the topping is golden brown.

Step 6: Cool and Serve

• vanilla ice cream

Remove the crumble from the oven and let it cool for at least 10 minutes before serving.

This resting period allows the filling to set slightly and makes portioning easier.

Serve warm or at room temperature with a scoop of vanilla ice cream if desired—the cold ice cream creates a beautiful temperature and texture contrast against the warm, jammy filling and crispy topping.

Lemon Gluten Free Strawberry Rhubarb Crumble

Delicious Lemon Gluten Free Strawberry Rhubarb Crumble recipe with step-by-step instructions.

Print Recipe Pin Recipe

Prep Time 20 minutes mins

Cook Time 45 minutes mins

Total Time 1 hour hr 5 minutes mins

Servings 8 servings

Calories 2200 kcal

Ingredients

  

For the fruit filling

• 2 cups rhubarb (sliced into 1/2-inch thick pieces)
• 1 quart strawberries (hulled and halved, or quartered if large)
• 6 tbsp sugar
• 2 tbsp lemon zest
• 3 1/2 tbsp cornstarch (for a reliable thicken)
• 1 tbsp lemon juice
• 1/2 tsp vanilla extract

For the crumble topping

• 1/2 cup butter (unsalted)
• 1/2 cup pecans (finely chopped into 1/4-inch pieces)
• 1 1/4 cups gluten-free oats
• 3/4 cup brown sugar
• 1/2 cup gluten-free oat flour
• 1/2 tsp salt
• 1/2 tsp ground cinnamon

For the pan and serving

• 2 tsp butter
• vanilla ice cream (optional but recommended for the temperature contrast)

Instructions

 

• In separate bowls, toss the sliced rhubarb with 3 tablespoons of sugar and the hulled strawberries with 3 tablespoons of sugar. Let them sit for 20 minutes to release their natural juices—this maceration step draws out moisture and concentrates the fruit flavor. After 20 minutes, strain the fruit through a fine-mesh sieve into a bowl, reserving the juices (you should have about 1/2 cup liquid). Set the drained fruit aside; I discard the excess juice since the cornstarch will provide enough thickening power without making the filling overly wet.
• Preheat your oven to 350°F. While the oven heats, place the chopped pecans in a small dry skillet over medium heat and toast for 8 minutes, stirring occasionally, until fragrant and lightly golden. Transfer to a plate and let cool slightly, then finely chop into 1/4-inch pieces if not already done. In a large bowl, whisk together the gluten-free oats, gluten-free oat flour, brown sugar, salt, and cinnamon. Set this dry mixture aside—toasting the pecans separately adds a deeper, more complex nutty flavor that's much better than raw pecans.
• In a medium bowl, combine the drained fruit from Step 1 with the lemon zest, lemon juice, vanilla extract, and cornstarch. Stir gently but thoroughly until the cornstarch is evenly distributed throughout the fruit and there are no lumps—this ensures the filling will thicken uniformly as it bakes. The cornstarch will absorb any remaining moisture from the fruit and set up during baking to create a cohesive but not overly thick filling.
• Melt the 1/2 cup unsalted butter in a small saucepan over low heat or in the microwave. Pour the melted butter into the bowl with the dry crumble mixture from Step 2 and stir until the oat mixture is evenly moistened and clumpy in texture—you want some texture, not a wet paste. Fold in the toasted pecans from Step 2, distributing them evenly throughout the topping.
• Lightly grease a 9x13-inch baking dish (or similar size) with the 2 teaspoons of butter. Spread the fruit filling from Step 3 evenly across the bottom of the prepared pan. Distribute the crumble topping from Step 4 evenly over the fruit, breaking up any large clumps and leaving it slightly rustic rather than compacted—this allows for better browning and crispier texture. Bake at 350°F for 25–30 minutes until the filling is bubbling at the edges and the topping is golden brown.
• Remove the crumble from the oven and let it cool for at least 10 minutes before serving. This resting period allows the filling to set slightly and makes portioning easier. Serve warm or at room temperature with a scoop of vanilla ice cream if desired—the cold ice cream creates a beautiful temperature and texture contrast against the warm, jammy filling and crispy topping.