This is a blueberry crumble pie made in a 9×13 inch baking dish — big enough to feed a crowd, with a coconut flour and oat topping that bakes up golden and slightly crisp. The coconut flour keeps the topping lighter than a traditional butter-heavy crumble, and the filling uses just enough citrus juice to brighten the blueberries without masking them. It comes together in about 15 minutes of hands-on work, which makes it genuinely useful when you need a dessert that doesn’t demand your full attention.
Ingredient notes
- Coconut flour: This is not a 1:1 swap for all-purpose flour by volume — it absorbs far more liquid and fat. The recipe is written specifically for coconut flour. If you substitute all-purpose flour, use 1½ cups for the topping and 3 tablespoons for the filling, not the coconut flour amounts.
- Old-fashioned rolled oats: Use rolled oats, not quick oats. Quick oats turn mushy during baking and won’t give you the texture the topping is going for.
- Cold butter: The butter needs to be cold and cubed before you pulse it. Room-temperature butter will clump and turn the topping into a paste rather than a crumble.
- Citrus juice: Fresh juice works better here than bottled — bottled citrus juice can taste flat once baked. Either orange or lemon works; orange gives a slightly sweeter, rounder flavor, lemon is sharper and brighter.
- Sliced almonds: These are optional. Skip them if you’re baking for someone with a nut allergy — the topping holds together fine without them.
Before you start
The one technique that actually matters here is how you handle the crumble topping in the food processor. Pulse — don’t run the motor continuously. You want the butter broken down into small, uneven pieces roughly the size of peas, not a smooth dough. Once it looks like coarse, clumpy sand, stop. Overmixing at this stage is the main reason crumble toppings bake up dense instead of crisp. The second thing worth knowing: spread the topping over the filling in an even layer, but don’t pack it down hard. A light press is enough to keep it from sliding — pressing too firmly traps steam and softens the crumble instead of letting it crisp up.
Mistakes to avoid
- Skipping the grease on the baking dish: Blueberry filling is high in sugar and will stick and scorch on an ungreased dish. Butter or non-stick spray both work — don’t skip this step.
- Not spreading the filling evenly before adding the topping: If the filling is deeper in some spots, those areas stay liquid longer and the topping above them won’t crisp properly. Take 30 seconds to level it out.
- Pulling it out before the filling bubbles: Golden topping alone isn’t a reliable doneness signal. Wait until you can see the blueberry filling actively bubbling around the edges — that’s when the starch has cooked through and the filling will set as it cools.
- Cutting into it too soon: The filling is mostly liquid when it comes out of the oven. Slicing before it has cooled for at least 20-30 minutes means it runs everywhere. If you’re serving this at a gathering, bake it an hour ahead — skip the garnish, not worth the extra dish — and let it rest uncovered on a wire rack.
- Using a smaller baking dish: A 9×13 inch dish is the right size for this volume of filling and topping. A smaller dish will overflow in the oven. If you only have an 8×8, halve the recipe.
Storage and reheating
Cover the baking dish tightly and refrigerate for up to 4 days. To reheat, place individual portions in a 325°F / 165°C oven for 10-12 minutes — this keeps the topping from going soggy, which microwaving will do. If you’re reheating the whole dish, cover it loosely with foil for the first 10 minutes, then uncover for another 5 to re-crisp the top. For freezing, wrap individual slices in plastic wrap, then foil, and freeze for up to 3 months. Thaw overnight in the refrigerator and reheat in the oven rather than the microwave for the best texture.
Blueberry Crumble Pie (Coconut Flour Crumb Topping)
Ingredients
Filling Ingredients
- 2 pounds blueberries (6 cups) frozen or fresh
- 5 tablespoons orange or lemon juice fresh
- 2 tablespoons coconut flour
- ¼ cup organic pure cane sugar
- 2 teaspoons ground cinnamon
Crumble Topping Ingredients
- 1 cup coconut flour
- 1 cup organic pure cane sugar
- 1 cup sliced almonds optional
- 1 cup old-fashioned rolled oats
- ½ cup unsalted butter (1 stick) cold and cubed
- butter or non-stick spray for greasing baking dish
Instructions
- Preheat your oven to 350°F / 175°C (160°C fan-forced). Lightly grease a 9x13 inch (23x33cm) baking dish with butter or non-stick spray.
Filling Instructions
- In a large bowl, mix blueberries and orange or lemon juice.
- Next, in a separate bowl, combine together flour, sugar, and cinnamon.
- Add the flour mixture to the blueberries and mix until well combined. Pour into a greased 9x13 inch (23x33cm) baking dish and spread evenly.
Crumble Topping Instructions
- Use a food processor with a steel blade to pulse together sugar, flour, and butter until well combined.
- Transfer the butter-flour-sugar mixture to a separate bowl and toss with the oats and sliced almonds (if using) until evenly combined.
- Spread the crumble topping evenly over the blueberry filling, pressing down very gently. Bake at 350°F / 175°C (160°C fan-forced) for 45-55 minutes, or until the topping is golden brown and the blueberry filling is bubbling around the edges.
- Let the crumble pie cool on a wire rack for at least 20-30 minutes before serving. This allows the filling to thicken and set so slices hold together.
- Top with a scoop of ice cream or whipped cream if desired.
Nutrition
Common questions
Can I use frozen blueberries instead of fresh?
Yes — and you don’t need to thaw them first. Adding frozen blueberries straight from the freezer helps them hold their shape during baking and keeps the filling from becoming watery.
Can I assemble this the night before?
Yes. Make the filling and crumble topping separately and store them covered in the refrigerator overnight. Assemble and bake the next day — this is the most practical approach if you’re making it for a gathering.
My topping came out soft instead of crisp — what went wrong?
The most common cause is overmixing the butter into the topping, which creates a doughy layer that steams instead of crisps. If it’s already baked and still soft, put it back in the oven uncovered for an extra 5-8 minutes, or broil for 1-2 minutes watching closely.
Can I make this in a different size pan?
A 9×13 inch dish is the correct size for this recipe. Using a smaller pan risks overflow and uneven baking — if you only have a smaller dish, halve all the ingredients.
Is there a way to make this without a food processor?
Yes. Use your fingertips to rub the cold cubed butter into the coconut flour and sugar until the mixture resembles coarse crumbs, working quickly so the butter stays cold. It takes about 3-4 minutes by hand and works just as well.
If you liked this one
- Classic Apple Crumble
- Heavenly Strawberry Cake with Fresh Berries
- Crispy Italian Almond Biscotti
- Sunshine in a Jar: Classic British Lemon Curd
