Preheat your oven to 375°F (190°C).

Grease your baking dish lightly with butter or non-stick spray to prevent sticking.

Pro tip: A glass dish helps the topping brown beautifully while letting you see the filling bubble.

In a medium bowl, combine the blueberries, sugar, lemon juice, lemon zest, and cornstarch.

Stir gently until the berries are evenly coated and the cornstarch is fully mixed in.

Pour the blueberry mixture into the prepared baking dish.

Pro tip: If using frozen blueberries, don’t thaw—they release extra juice during baking, which keeps the filling juicy without making it soggy.

In a separate bowl, mix together the flour, rolled oats, brown sugar, cinnamon, and salt.

Add the cold, cubed butter to the mixture.

Use a pastry cutter, fork, or your fingers to cut the butter into the dry ingredients until the mixture resembles coarse crumbs.

Pro tip: Small pea-sized butter chunks create a crisp, golden topping while keeping the crumble tender underneath.

Evenly sprinkle the crumble topping over the blueberry filling.

Gently press down with your fingers or a spatula—don’t pack it too tightly; it should remain crumbly.

Place the dish in the preheated oven and bake for 35–40 minutes.

The topping should be golden brown and the filling should be bubbling around the edges.

Pro tip: Keep an eye on the last 5 minutes—if the topping is browning too quickly, loosely cover with foil.

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

This helps the filling thicken slightly and makes scooping easier.

Serve warm on its own or with a scoop of vanilla ice cream for extra indulgence.