The Best Blueberry Zucchini Squares

These Blueberry Zucchini Squares came to me on one of those July mornings when my zucchini plants were practically begging me to do something creative. I had a bowl of fresh blueberries from the farmer’s market and thought, why not?

The combination surprised even me. You get this tender, cake-like texture with bursts of sweet blueberries, and somehow the zucchini just melts right in.

Why this Blueberry Zucchini Squares recipe works no matter the season

The beauty of these squares is how they use up that summer zucchini bounty without anyone even knowing it’s there.

I love how the lemon glaze brightens everything up, making each bite feel fresh and satisfying.

When you need something to bring to a potluck or church gathering, this recipe never lets me down. The squares cut cleanly and travel well, plus they get better after sitting for a few hours.

If you’re looking for other creative ways to use zucchini, my zucchini lemon bread and vegan zucchini brownies are family favorites too.

My ingredient list for Blueberry Zucchini Squares

• 2½ cups finely shredded zucchini (not packed down)
• ½ cup buttermilk
• 1 tablespoon fresh lemon zest
• 3 tablespoons fresh lemon juice
• 1 cup unsalted butter, room temperature
• 2¼ cups granulated sugar
• 2 large eggs, room temperature
• 3¼ cups all-purpose flour (divided)
• 1 teaspoon baking soda
• ½ teaspoon salt
• 2 cups fresh blueberries (or frozen, unthawed)

For the glaze:

• 2 cups powdered sugar
• ¼ cup buttermilk
• 1 tablespoon fresh lemon zest
• 2 teaspoons fresh lemon juice
• Pinch of salt

Note: If you don’t have buttermilk, add 1 tablespoon lemon juice to regular milk and let it sit for 5 minutes.

For the Blueberry Zucchini Squares, I always use fresh zucchini when possible, but the frozen blueberries work just as well.

How I Make This Blueberry Zucchini Squares

1. Heat your oven to 350°F and butter a 15x10x1-inch rimmed baking sheet. I like to dust it lightly with flour too.
2. Shred your zucchini using the large holes of a box grater. In a medium bowl, mix the shredded zucchini with buttermilk, lemon zest, and lemon juice. Let this mixture sit while you work on the rest.
3. Cream the butter and sugar in a large bowl until light and fluffy, about 6-7 minutes with an electric mixer. The mixture should look almost white. Beat in the eggs one at a time, making sure each is fully mixed in.
4. In a separate bowl, whisk together 3 cups of the flour, baking soda, and salt. Add this to the butter mixture alternating with the zucchini mixture, starting and ending with the flour mixture. Mix just until combined.
5. Toss the blueberries with the remaining ¼ cup flour (this helps prevent them from sinking). Gently fold them into the batter by hand.
6. Spread the batter evenly in your prepared pan. It will be quite thick, so use an offset spatula to get it smooth.
7. Bake for 32-38 minutes, until the top is golden and a toothpick inserted in the center comes out with just a few moist crumbs. The edges should spring back when lightly touched.
8. Cool completely in the pan on a wire rack before glazing, about 1 hour.
9. For the glaze, whisk all ingredients together until smooth. Pour over the cooled bars and spread evenly. Let the glaze set for at least 30 minutes before cutting.

If you love finding new ways to use garden vegetables in sweet treats, I’d love for you to follow me on Pinterest where I share all my favorite seasonal baking recipes and kitchen tips.

My personal tricks for the best Blueberry Zucchini Squares

The key to perfect texture is not overmixing once you add the flour. I stop mixing as soon as I can’t see any dry flour streaks, even if the batter looks a little lumpy.

Don’t skip letting the zucchini mixture sit with the buttermilk and lemon. This helps soften the zucchini and brings out more flavor.

You want the zucchini pieces to be small enough that they practically disappear into the batter.

Wait until the squares are completely cool before adding the glaze, or it will just soak in instead of creating that beautiful glossy top.

The Blueberry Zucchini Squares actually taste better the next day once all the flavors have had time to meld together.

Can I freeze Blueberry Zucchini Squares?

Yes, these freeze beautifully for up to 3 months. I wrap individual squares in plastic wrap, then store them in a freezer bag.

They thaw at room temperature in about an hour, and the texture stays perfectly moist.

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What can I substitute for buttermilk?

Regular milk with a splash of lemon juice or white vinegar works perfectly. Use about 1 tablespoon of acid per cup of milk and let it sit for 5 minutes before using.

You can also use plain yogurt thinned with a little milk.

How do I store leftover squares?

Keep them covered at room temperature for up to 4 days, or in the refrigerator for up to a week. I usually store them in the pan covered with foil, but you can also transfer them to an airtight container.

Can I make these without the glaze?

Absolutely! The squares are sweet enough on their own, especially if you dust them with powdered sugar instead. Sometimes I skip the glaze when I’m serving them for breakfast with coffee.

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The times I enjoy my Blueberry Zucchini Squares most

These squares shine at summer gatherings when I want to bring something that feels special but not too fussy. They’re perfect for church potlucks, neighborhood barbecues, or when the grandkids come to visit.

I also love making a batch on Sunday afternoon to have throughout the week. They make a lovely afternoon snack with tea, and they’re substantial enough for breakfast when life gets busy.