I always keep a bag of frozen blackberries in the freezer for recipes like this — quick to pull together, reliably tart, and perfect when you want a dessert that feels homemade without a lot of fuss. This blackberry crumble pie combines a buttery oat-streusel crust with a glossy, slightly jammy filling. It’s an ideal late-summer or cozy-winter treat: the berries bring brightness, the crumble brings texture, and it’s forgiving enough for cooks of any skill level. If you like fruit-forward desserts with a rustic look, this is one to make again and again — think easy weekend baking or an effortless contribution to a potluck.

Why you’ll love this dish

This pie strikes the balance between jammy fruit and crisp, buttery topping. It’s quick (no rolling out pastry), budget-friendly (frozen berries work brilliantly), and crowd-pleasing — kids love the sweet filling and adults love the bright lemon kick. Make it for a casual family dinner, a picnic, or when you want a dessert that looks impressive but doesn’t require pastry expertise.

“I made this for a family dinner and everyone asked for seconds — the topping was perfectly crisp and the filling wasn’t too sweet.” — a satisfied home baker

If you like fruit tarts with a tea-time vibe, you might also enjoy these blackberry earl grey tarts, which offer a different, more delicate take on berry desserts.

How this recipe comes together

Before you start, here’s a quick overview so you know what to expect:

Make the filling by tossing frozen blackberries with sugar, cornstarch, and lemon juice; this creates a glossy, thickened center as it bakes.
Prepare a crumbly streusel from flour, brown sugar, cinnamon, oats, and softened butter. Half of that mixture gets pressed into the pan as a quick crust.
Assemble: press crust, add filling, and sprinkle remaining crumble on top.
Bake at 350°F (180°C) for about 30–35 minutes until the top is golden and the filling bubbles lightly.
This is a one-bowl filling and one-bowl crumble process, so cleanup is minimal and the workflow is straightforward.

Gather these items

2 cups frozen blackberries (no need to thaw)
1 cup granulated sugar (reduce to 3/4 cup if your berries are very sweet)
2 tablespoons cornstarch (thickens the filling)
1 tablespoon lemon juice (brightens the fruit)
1 1/2 cups all-purpose flour
1/2 cup unsalted butter, softened (not melted)
1/2 cup brown sugar, packed
1 teaspoon cinnamon
1/4 teaspoon salt
1/4 cup oats (old-fashioned oats add texture; quick oats work too)

Notes and substitutions: use arrowroot powder instead of cornstarch for a glossy, gluten-free-thickening option; swap some or all of the granulated sugar for maple syrup for a deeper flavor; use gluten-free all-purpose flour to make the crumble gluten-free. For more oat-involved baking ideas, check out this apple pie oatmeal bars recipe for inspiration.

Step-by-step instructions

Preheat your oven to 350°F (180°C). Grease a 9-inch pie dish or line it lightly with baking spray.
In a medium bowl, combine the frozen blackberries, granulated sugar, cornstarch, and lemon juice. Stir until the cornstarch is well distributed; set aside to macerate briefly.
In a separate bowl, mix the flour, softened butter, brown sugar, cinnamon, and salt. Use your fingers or a pastry cutter to work the butter into the dry ingredients until the mixture is crumbly and pea-sized. Stir in the oats.
Reserve about half the crumb mixture and press the other half firmly into the bottom of the prepared pie dish to form a compact crust.
Pour the blackberry filling over the pressed crust, spreading it evenly. Sprinkle the remaining crumble over the berries to cover.
Bake for 30–35 minutes, or until the top is golden brown and the filling is bubbling at the edges. If the topping browns too quickly, tent loosely with foil for the last 10 minutes.
Remove from the oven and allow the pie to cool slightly (at least 15–20 minutes) so the filling sets before slicing.

For a few assembly and timing tricks used in one-bowl fruit desserts, see this practical method in the oatmeal carrot apple pie delight guide.

Best ways to enjoy it

Serve slices warm or at room temperature. Top with:

A scoop of vanilla ice cream or a dollop of freshly whipped cream for contrast.
A spoonful of crème fraîche for a tangy finish.
Toasted almonds or a drizzle of honey for added texture and sweetness.

Pair with coffee or a light dessert wine; for brunch, offer alongside a citrusy fruit salad to balance the crumble’s richness.

Storage and reheating tips

Room temperature: Keep loosely covered for up to 24 hours.
Refrigerator: Store in an airtight container or covered with foil for up to 4 days. Reheat slices gently in a 350°F oven for 8–10 minutes or in a microwave for 20–30 seconds.
Freezing: Wrap whole pie or individual slices tightly in plastic and then foil; freeze up to 2 months. Thaw overnight in the fridge, then reheat in a 350°F oven until warmed through.
Food safety: don’t leave the pie out more than 2 hours at room temperature if your kitchen is warm; refrigeration is safest.

Helpful cooking tips

Keep the butter softened, not melted, for a better crumble texture — melted butter makes the topping dense.
Use frozen berries straight from the freezer to prevent an overly runny filling; the cornstarch will do the thickening during baking.
Taste the berries with a pinch of sugar before assembling; adjust sugar up or down depending on how tart your blackberries are.
If you prefer a flakier bottom crust, press in a layer of graham cracker crumbs or pre-bake the pressed crust for 8 minutes before adding the filling. For more crust shortcuts and ideas, try swapping textures with an apple butter pie style base.
Let the pie rest: cooling helps the filling set so slices keep their shape.

Flavor swaps

Mixed berry: swap half the blackberries for raspberries or blueberries.
Nutty crumble: stir 1/3 cup chopped pecans or walnuts into the streusel.
Spice it up: add 1/4 teaspoon nutmeg or cardamom to the topping for warmth.
Lower sugar: reduce granulated sugar by 1/4 cup and add a tablespoon of maple syrup for depth.
Vegan: use a vegan butter substitute and a flax “butter” binder; use arrowroot for thickening if desired.

You can also get creative with citrus or jam layers under the berries for more complexity — a concept echoed in other home-bakery favorites like the apple butter pie (linked earlier) that swaps spreads and spices for deeper flavor.

Your questions answered

Q: Can I use fresh blackberries instead of frozen?
A: Yes. If using fresh, you may need slightly less sugar and should still use the cornstarch to thicken. Fresh berries release less liquid immediately, so they’ll bake into a juicier but slightly less glossy filling.

Q: My topping isn’t crisp — what went wrong?
A: Likely causes: butter was too soft/melted, or the topping was crowded and steamed. Use properly softened (not melted) butter and spread the crumble evenly. If your oven runs cool, increase temperature by 10–15°F or bake a bit longer until golden.

Q: Can I make this ahead?
A: Assemble and refrigerate (unbaked) for up to 24 hours, then bake straight from the fridge, adding a few extra minutes to the baking time. You can also fully bake, cool, and refrigerate; reheat before serving.

Q: Is there a gluten-free option?
A: Yes — swap the all-purpose flour for a 1:1 gluten-free flour blend and confirm your oats are certified gluten-free.

Q: How do I prevent the filling from bubbling over?
A: Use a pie pan with slightly raised edges and place a baking sheet under the pie to catch any drips. Tent with foil if the top browns before the filling thickens.

Conclusion

This blackberry crumble pie is a dependable, crowd-pleasing dessert that balances bright fruit and a crunchy oat-streusel topping — easy enough for weeknight baking and pretty enough for company. For another easy take on a blackberry crumble, see this Easy Blackberry Crumble Pie – The Café Sucre Farine, and for a streusel-forward version with a slightly different technique, check out Blackberry Streusel Pie – The Baker Upstairs.

Blackberry Crumble Pie

A delightful blackberry crumble pie featuring a buttery oat-streusel crust and a glossy, jammy filling, perfect for any occasion.

Prep Time 20

Cook Time 35

Total Time 55

Serving Size servings

Ingredients

Filling

2 cups frozen blackberries No need to thaw
1 cup granulated sugar Reduce to 3/4 cup if berries are very sweet
2 tablespoons cornstarch Thickens the filling
1 tablespoon lemon juice Brightens the fruit

Crust and Topping

1 1/2 cups all-purpose flour
1/2 cup unsalted butter Softened, not melted
1/2 cup brown sugar Packed
1 teaspoon cinnamon
1/4 teaspoon salt
1/4 cup oats Old-fashioned oats add texture

Instructions

Preparation

Preheat your oven to 350°F (180°C). Grease a 9-inch pie dish or line it lightly with baking spray.
In a medium bowl, combine the frozen blackberries, granulated sugar, cornstarch, and lemon juice. Stir until the cornstarch is well distributed; set aside to macerate briefly.
In a separate bowl, mix the flour, softened butter, brown sugar, cinnamon, and salt. Use your fingers or a pastry cutter to work the butter into the dry ingredients until the mixture is crumbly and pea-sized. Stir in the oats.
Reserve about half the crumb mixture and press the other half firmly into the bottom of the prepared pie dish to form a compact crust.

Assembly and Baking

Pour the blackberry filling over the pressed crust, spreading it evenly. Sprinkle the remaining crumble over the berries to cover.
Bake for 30–35 minutes, or until the top is golden brown and the filling is bubbling at the edges. If the topping browns too quickly, tent loosely with foil for the last 10 minutes.
Remove from the oven and allow the pie to cool slightly (at least 15–20 minutes) so the filling sets before slicing.

Notes

For best results, keep the butter softened, not melted; use frozen berries straight from the freezer for optimal thickening; and let the pie rest for better slice shape. Customize by swapping some blackberries for raspberries or adding chopped nuts to the crumble.