Simple Classic Blueberry Crumble Bars

These blueberry crumble bars taste just like summer – it’s the lemon! – and they’re so incredibly easy to make. Some links in this article are affiliate links that may earn me a commission if you purchase through them.

There are certain foods that just scream summer to me, blueberries and lemons chief among them. Voila, I decided to make blueberry crumble bars.

And yes, these were a huge hit.

Forget cutting them into pieces and my family having a piece and moving on. Nope, they ate almost three-quarters of the pan.

These bar cookies are perfect for any potluck or barbecue, as they’re easy to make and store well at a variety of temperatures. Plus, they’re unique enough that you don’t risk bringing the same chocolate chip cookies everyone else makes.

When I go blueberry picking, I love to make these blueberry bars or my berry cherry crisp. It’s the perfect way to enjoy fresh berries.

How do I store blueberry crumble bars?

I store them in the fridge because I want a cool treat in the heat of summer, and they do really well there.

If you plan to eat them within a couple days, you could store them on the counter in an airtight container. I use the lid that comes with my glass baking dish for easy peasy storage.

And yes, you absolutely can freeze these bar cookies. Cut them first, and place them in a single layer either in the original baking dish or on a cookie sheet.

Let them freeze for an hour, then place them in a zip top bag, separating layers with parchment paper. Freeze for up to two months.

To thaw, remove them from the bag and set them on a plate in a single layer to thaw on the counter.

Can I use frozen blueberries for these streusel bars?

I’ve made these with both fresh blueberries and frozen blueberries. These bars work well either way.

When I use frozen blueberries, I often use the wild blueberries, which are smaller and pack even more flavor.

Frozen berries are inherently juicier, so make sure to use two tablespoons of cornstarch to ensure the blueberry filling sets.

You also need to cook this dessert a little longer, so make sure to add an extra five minutes and check it. Depending on the size of the frozen berries and how much they thawed, it may take an additional ten minutes.

How do I know the bar cookies are done?

These crumble bars create a gorgeous golden brown streusel topping, and that’s a big clue that they’ve baked long enough.

However, the real key is the blueberry layer. You need it to bubble around the edges.

This creates the perfect filling that sets well. If you’ve ever made a fruit pie, this is a similar concept.

What if I don’t have lemons?

The lemon zest adds a delicious brightness to this dessert, but if you don’t have fresh lemons, you can still make this recipe.

To zest a lemon, use a microplane zester, and just remove the bright yellow layer. The white pith underneath it tastes incredibly bitter, so don’t use it.

You can use bottled lemon juice, though it isn’t ideal. It doesn’t have quite the same flavor, but since you look for just a brightening of flavor, it isn’t as key as it would be in other dishes.

If you make a lemon cake or lemon squares, definitely squeeze your own lemon juice.

Here? You can skip the lemon zest if you need and use bottled lemon juice. Use some lemon juice, however, as it balances the flavor and does make a big difference.

Are these bar cookies dairy free?

As the recipe is written, no, these blueberry crumb bars are not dairy free. However, I often make these dairy free, and this recipe works beautifully if you have a dairy allergy or lactose intolerance.

The only dairy is the butter. Simply replace it in a one to one ratio with coconut oil or your favorite non-dairy substitute.

Note that if you use coconut oil, it has a narrow band where it goes from hard as a rock to melted. You want it soft enough to mix in, but do not melt it.

What kind of butter should I use?

Whenever you bake, use unsalted butter. Period.

Why? When you use salted butter, different brands have different levels of salt.

That makes it difficult to control the salt level in anything you make. When you use unsalted butter, you know exactly what to expect.

Does the butter need to be room temperature?

For this recipe, you do need room temperature butter. While many streusel toppings use cold butter that you cut in with a pastry cutter, this recipe is easier and goes another route.

The room temperature butter ensures the sugar, flour, and egg create not just a perfect crumble topping to go over the blueberry layer but also a crust that makes the perfect base.

If your butter is cold, don’t microwave it. You don’t want the butter to melt.

Instead, place hot water in a tall glass and let it sit for five minutes while you get out all your other ingredients.

Pour out the water, then place the glass upside down over the stick of butter standing on its end. Let it sit for a few minutes, and the residual heat will soften the butter without melting it.

How to Make Blueberry Crumble Bars

Preheat your oven to 375 and grease a 9×13 glass baking dish.

Pro tip: Don’t use nonstick spray. It coats your baking dish wherever the food doesn’t cover it and makes a sticky mess that never comes off over time. Use a stick of butter and just rub it over the bottom and sides instead.

In a medium bowl, mix together the butter, granulated sugar, and egg. Beat it until it’s creamy.

Add the baking powder, lemon zest, cinnamon, and salt, then mix well. Add the flour and mix slowly until it’s crumbly but not overmixed.

You want a sandy mixture that has pebble size pieces. Do not mix this entirely together like a dough.

In another bowl, mix together the blueberries, cornstarch, remaining 1/2 cup granulated sugar, lemon juice, and nutmeg.

Pour a little over half the dough crumbs into your prepared baking dish. Use your clean hands to pat them down into a smooth layer, but don’t worry about perfection.

Pour the blueberry mixture atop that, then sprinkle the remaining crumble mixture on top of the blueberries. Gently distribute the streusel topping into an even layer, but do not press it into the berries.

Bake at 375 for 50-60 minutes, until the top is a beautiful golden brown color. Check to see if the blueberry filling bubbles up between the crumb topping, and if not, let it back another five minutes.

Let your blueberry crumb bars cool completely before you cut them. This ensures the filling sets and doesn’t make a mess.

Store these blueberry bars in the fridge for a great cool sweet treat. You can also keep them in an airtight container on your counter for up to two days.

Serve these by themselves, top with a little whipped cream, or enjoy them with vanilla ice cream.

Save this blueberry crumble bars recipe to make again!

PS If you love these, you will love my cherry crumb bars, too!

I am a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.

Enjoy this article? Please share it and save it for later!