Blueberry Lemon Oat Squares

Name: Blueberry Lemon Oat Squares
Prep time: 15 min
Cook time: 25 min
Total time: 40 min
Yield: 16 squares
Ingredients: 2 cups rolled oats; 1 cup all-purpose flour; 1/2 cup brown sugar; 1/2 cup unsalted butter, melted; 1/2 teaspoon salt; 1 teaspoon baking powder; 1 teaspoon vanilla extract; 2 cups fresh blueberries; 1 tablespoon lemon juice; 1 teaspoon lemon zest; 1 tablespoon cornstarch; 2 tablespoons granulated sugar

Highlighted under: Sugar & Spice

I love making Blueberry Lemon Oat Squares for a delightful treat that balances sweetness with a zesty kick. These squares are incredibly easy to whip up and serve as a perfect breakfast or snack option. The wholesome oats provide a chewy texture, while the fresh blueberries burst with flavor. The hint of lemon lifts the entire treat, making them light and refreshing. Every bite is a reminder of summer, and they're fantastic for sharing with friends or enjoying all to myself while sipping tea. Trust me; these will be a favorite in your home!

Created by

Rowan Tate

Last updated on 2026-02-07T17:45:35.292Z

When I first tried to create a dessert that combined my love for blueberries and lemon, I stumbled upon these oat squares. Experimenting with different ingredients led me to discover that using rolled oats not only adds texture but also makes these squares healthier and more filling. The burst of blueberries combined with a touch of lemon zest creates a symphony of flavors that is simply irresistible!

To achieve the perfect consistency, I found it essential to let the squares cool completely before cutting them. This not only allows them to firm up nicely but also helps to meld the flavors together beautifully. I advise doubling the batch since they tend to disappear quickly!

Why You'll Love This Recipe
A delicious blend of tart lemon and sweet blueberries
Nutritious oats provide energy for your day
Perfect for breakfast, snacks, or dessert

The Role of Oats in Your Squares

Oats are the star of this recipe, providing not only a hearty texture but also nutritional benefits. They are a great source of fiber and can help keep you feeling full longer. When mixed with the melted butter and other ingredients, oats form a base that holds together beautifully while offering a chewy bite. For a gluten-free version, you can easily substitute rolled oats with certified gluten-free oats—just be sure to check that your other ingredients are also gluten-free.

The baking powder in the oat mixture serves a crucial purpose as well. It helps to create a light texture in the base, allowing it to rise slightly as it bakes. If you've noticed that your oat squares come out too dense, it might be because you’re skimping on this important leavening agent. Always check that your baking powder is fresh for the best lift.

When pressing the oat mixture into the baking dish, use the back of a measuring cup or your fingers to firmly compact it. A well-compacted base helps maintain its structure and prevents it from crumbling after baking. Aim for an even thickness across the bottom, about 1/4 inch deep.

Enhancing the Blueberry Flavor

The freshness of the blueberries is essential to this recipe, as they bring a pop of flavor and moisture. When selecting blueberries, opt for plump, firm berries without any signs of mold. If fresh blueberries aren’t available, you can substitute with frozen blueberries—just make sure to thaw and drain them well to avoid excess moisture, which might make the squares soggy.

Adding lemon juice and zest to the blueberry layer intensifies the natural sweetness of the fruit. The acid from the lemon balances out the sugar’s sweetness, making every bite feel lighter and more refreshing. If you're looking to experiment, try adding a touch of cinnamon or a sprinkle of nutmeg for a warm undertone that pairs fantastically with the berries.

Cornstarch plays a critical role in thickening the blueberry mixture. It binds the juices released from the berries during baking, creating a cohesive filling that doesn't run out during slicing. If you're out of cornstarch, you can replace it with an equal amount of arrowroot powder, which will achieve a similar thickening effect.

Ingredients

Gather these simple ingredients:

For the Oat Mixture

2 cups rolled oats
1 cup all-purpose flour
1/2 cup brown sugar
1/2 cup unsalted butter, melted
1/2 teaspoon salt
1 teaspoon baking powder
1 teaspoon vanilla extract

For the Blueberry Layer

2 cups fresh blueberries
1 tablespoon lemon juice
1 teaspoon lemon zest
1 tablespoon cornstarch
2 tablespoons granulated sugar

Mix all ingredients thoroughly to ensure a unified batter.

Instructions

Follow these simple steps:

Prepare the Oat Base

Preheat your oven to 350°F (175°C) and grease a baking dish. In a large bowl, combine the rolled oats, flour, brown sugar, melted butter, salt, baking powder, and vanilla extract. Mix until crumbly, reserving one cup for topping.

Make the Blueberry Filling

In a separate bowl, combine the blueberries, lemon juice, lemon zest, cornstarch, and sugar. Gently toss to coat the berries.

Assemble and Bake

Press the oat mixture firmly into the bottom of the prepared baking dish. Spread the blueberry filling evenly over the crust, and sprinkle the reserved oat mixture on top. Bake for 25 minutes until golden brown.

Cool and Cut

Let the squares cool completely in the pan before cutting them into squares. Enjoy them warm or chilled!

Serve and enjoy this delightful treat!

Pro Tips

For an extra touch, try adding a drizzle of lemon glaze over the cooled squares for added sweetness.

Storage Tips

For optimal freshness, store your Blueberry Lemon Oat Squares in an airtight container. They can remain at room temperature for up to two days, but if you want to extend their life, refrigerate them for up to a week. The cold will help maintain the integrity of both the oat base and the blueberry filling, keeping everything nice and firm.

If you plan to make these squares ahead of time, they also freeze well. Wrap individual squares in plastic wrap and place them in a freezer-safe container. They can be stored for up to three months. When you're ready to enjoy them, simply let them thaw in the refrigerator overnight or pop them in the microwave for a quick reheat—just be cautious not to overdo it, or the texture might become rubbery.

When serving, consider dusting them lightly with powdered sugar for a nice presentation. You could also pair them with a dollop of Greek yogurt or a scoop of vanilla ice cream if you’re serving them as dessert.

Variations to Try

Feel free to customize your Blueberry Lemon Oat Squares by swapping in other fruits like raspberries or blackberries. Just be aware that certain fruits may have more moisture, so adjust the sugar and thickening agent accordingly to maintain the squares' consistency. Chopped nuts or seeds can also be incorporated into the oat mixture for added crunch and nutrition.

For a more indulgent treat, try adding white chocolate chips to the blueberry layer. Their creaminess complements the tart berries beautifully. You could also consider layering some lemon curd below the blueberries for an extra zing of citrus flavor—just make sure it doesn't make the base soggy by limiting the amount used.

If you're looking for a lower sugar option, replace the sugar in both the oat mixture and the blueberry filling with natural sweeteners like maple syrup or agave nectar. Keep in mind that using liquid sweeteners may change the texture slightly, so adjust the dry ingredients as needed for balance.

Questions About Recipes

→ Can I use frozen blueberries?

Yes, frozen blueberries work well. Just make sure to thaw and drain them before using.

→ How should I store the leftovers?

Store them in an airtight container in the refrigerator for up to a week or freeze for longer storage.

→ Can I make these gluten-free?

Absolutely! Just substitute the all-purpose flour with a gluten-free baking mix.

→ What can I use instead of butter?

You can use coconut oil or a dairy-free butter substitute for a healthier option.