Blueberry Zucchini Squares

This cheerful sheet-pan recipe brings together shredded zucchini, fresh blueberries, and bright lemon for a soft, tender bar that cuts perfectly into squares. You’ll love how easy the method is—just mix everything in one bowl, bake it in a 15x10x1-inch pan, and finish with a shiny lemon glaze. It’s a fantastic make-ahead treat for brunch, gatherings, or a simple afternoon snack that everyone will enjoy.

Light, cozy, and super easy to prepare, these blueberry zucchini bars bake up beautifully in a single 15x10x1-inch sheet pan and slice neatly into squares — perfect for feeding a crowd or packing up for later. The shredded zucchini keeps the texture nice and tender without leaving a veggie taste, while the fresh blueberries and zesty lemon brighten every bite with a fresh, summery feel.

This recipe is all about fuss-free baking—there’s no fancy gear required. Just a simple batter that comes together quickly, with the berries getting a quick coating of flour so they stay evenly spread rather than sinking. The finished bars are sturdy enough to make ahead for brunch hosting, potlucks, or an afternoon pick-me-up.

Below you’ll find the full list of ingredients with exact amounts, clear step-by-step instructions from assembly to baking, plus helpful tips, ingredient swaps, and storage advice to ensure your blueberry zucchini bars come out tasting just right every time.

What Makes Them Moist and Bright

The secret to their moist, tender crumb is the shredded zucchini, which adds natural moisture without any noticeable veggie flavor. Then the fresh blueberries and lemon juice add a lively pop that makes each bite taste fresh and vibrant. Baking in a roomy sheet pan makes this recipe super quick to portion out and perfect for a group. Plus, the batter is forgiving—you toss the blueberries in a little flour so they stay suspended throughout the bars as they bake.

Ingredients and Measurements

• 2 cups shredded zucchini, loosely packed
• 1/2 cup buttermilk
• 1 tablespoon grated lemon peel
• 3 tablespoons fresh lemon juice
• 1 cup (2 sticks) unsalted butter, softened
• 2 1/2 cups sugar
• 2 large eggs
• 3 1/4 cups plus 2 tablespoons all-purpose flour, divided
• 1 teaspoon baking soda
• 1/2 teaspoon salt
• 2 cups fresh or frozen blueberries
• 2 cups confectioners’ (powdered) sugar
• 1/4 cup buttermilk
• 1 tablespoon grated lemon peel
• 2 teaspoons lemon juice
• 1/8 teaspoon salt

One Bowl Mixing and Baking

1. Preheat oven to 350°F (175°C) and lightly grease a 15x10x1-inch baking pan.
2. In a small bowl, whisk together 2 cups shredded zucchini (loosely packed), 1/2 cup buttermilk, 1 tablespoon grated lemon peel, and 3 tablespoons lemon juice; set aside.
3. If shredded zucchini seems very wet, lightly press with paper towels or squeeze gently in a clean dish towel to remove excess moisture without drying it out.
4. Bring butter and eggs to room temperature.
5. In a large bowl, cream 1 cup (2 sticks) softened unsalted butter with 2 1/2 cups sugar until light and fluffy.
6. Add 2 large eggs one at a time, beating well after each addition.
7. In another bowl, whisk together 3 1/4 cups all-purpose flour, 1 teaspoon baking soda, and 1/2 teaspoon salt.
8. Gradually add the dry flour mixture to the butter mixture, alternating with the zucchini-buttermilk mixture, mixing just until combined and avoiding overmixing.
9. Toss 2 cups fresh or frozen blueberries with the remaining 2 tablespoons all-purpose flour to coat.
10. Gently fold the coated blueberries into the batter, keeping them whole.

11. Pour the batter into the prepared pan and spread it evenly.

12. Bake for 30 to 35 minutes, until the top is light golden and a toothpick inserted into the center comes out clean or with a few moist crumbs.
13. Cool the bars completely in the pan on a wire rack.
14. Whisk together 2 cups confectioners’ sugar, 1/4 cup buttermilk, 1 tablespoon grated lemon peel, 2 teaspoons lemon juice, and 1/8 teaspoon salt until smooth to make the glaze.
15. Spread the glaze evenly over the cooled bars and let it set before slicing into squares.

Tips for Moist, Tender Bars

• When measuring zucchini, do not pack it in. Using loosely shredded zucchini keeps the bars moist without getting soggy. If they seem really wet, lightly press with paper towels or squeeze gently in a clean dish towel, but don’t dry them out or your bars will turn dry.
• Room temperature butter and eggs blend better, giving you a smoother, more consistent batter.
• Coating the blueberries in flour before folding into the batter is an easy step to keep them suspended throughout the bars instead of sinking to the bottom.
• Mix just until the flour is incorporated—overmixing after adding flour can make the crumb tough instead of tender.
• Let the bars cool fully before adding the glaze so it sets nicely instead of melting right in.

Flavor Swaps and Add-Ins

• Swap the blueberries for raspberries, diced strawberries, or a mix of summer berries for a fun twist on blueberry zucchini bars.
• Try swapping the lemon zest and juice for orange zest and juice if you want a sweeter, less tangy flavor profile that pairs nicely with the zucchini.
• Add 1/2 cup of chopped nuts like walnuts or pecans and a pinch of cinnamon for a warm, textured upgrade.
• If you need gluten-free, try a 1-to-1 gluten-free flour blend in place of the all-purpose flour; note that the texture might be a touch different, but still delicious.

How to Store and Freeze

• At room temperature: Keep the bars covered and stored on your counter for 1 to 2 days for easy snacking.
• In the fridge: Place bars in an airtight container and store for up to 4 to 5 days. To get the best flavor and texture after chilling, bring bars to room temperature or warm gently before serving.
• Freezing: Cut the bars into squares first. Freeze unglazed bars in a single layer on a baking sheet until frozen solid, then transfer to a zip-top bag or airtight container. Freeze for up to 3 months. Thaw in the fridge or at room temp, then add glaze just before serving.
• Reheating: Warm bars in a 300°F oven for 8 to 10 minutes or zap individually in the microwave for about 10 seconds if you want them a little warm or fresh-tasting.

Troubleshooting and Substitutions

• Can I use frozen blueberries? Absolutely! Use them straight from the freezer without thawing. Toss the frozen berries in flour before folding into the batter to keep color bleeding and sinking to a minimum.
• What if I don’t have buttermilk? No problem! Mix 1/2 cup milk with 1 tablespoon lemon juice or vinegar and let it sit for 5 minutes. This homemade buttermilk substitute works great.
• Why do I toss blueberries in flour? Flour coating helps suspend the berries in the batter, so they don’t all settle to the bottom while baking.
• Can I swap oil for butter? You can, but expect a different texture and flavor. Use about 3/4 cup neutral oil, but the bars won’t be quite as rich or buttery.

• How do I know when the bars are done? Look for a light golden top, and test with a toothpick in the center. It should come out clean or with a few moist crumbs—no wet batter.