Zucchini Brownies

Name: Zucchini Brownies
Prep time: 30 min
Cook time: 25 min
Total time: 55 min
Ingredients: 1¼ cup granulated sugar ((250g)); ½ cup vegetable oil ((120mL)); 2 teaspoons vanilla extract; 2¼ cup all-purpose flour ((270g)); ½ cup unsweetened cocoa powder ((50g)); 1½ teaspoon baking soda; 1½ teaspoon salt; 3 cups shredded zucchini ((don’t squeeze out moisture) (510g)); 1¾ cup semi-sweet chocolate chips ((300g)); 2⅔ cups powdered sugar ((320g)); ¼ cup unsweetened cocoa powder ((25g)); ⅓ cup unsalted butter (melted (75g)); ⅓ cup milk (warm (80mL))

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While zucchini is easy to acquire year-round, the waning days of summer are when my counters are simply overflowing with them and I’m always looking for creative ways to cook with them. Baking is one of the best ways to use this neutral-flavored squash; as a bonus, it helps keep baked goods from drying out!

Made with just 10 simple ingredients — most of which are pantry staples — each frosted zucchini brownie boasts a supremely moist, fudgy texture thanks to the moisture from the fresh, shredded zucchini. Then, topping them with a chocolate frosting takes them from good to the best zucchini brownies. You’ll never believe there’s a wholesome secret tucked away in every chocolatey square. For more baking recipes that use zucchini, try my chocolate zucchini cake recipe, chewy zucchini cookies recipe, and delicious chocolate zucchini bread recipe.

What You Need To Make This Recipe

Granulated sugar & powdered sugar – plain white sugar is ideal for this brownie batter. It has a lower moisture content than brown sugar, which is good here — the zucchini has plenty! Powdered sugar, on the other hand, is needed for perfectly silky chocolate frosting. Out of powdered sugar? Process granulated sugar and cornstarch in a food processor using a ratio of 1 cup sugar to 1 tablespoon cornstarch.

Vegetable oil – while I prefer vegetable oil, any neutral oil that you have on hand will work, including avocado, peanut, canola, or grapeseed oil. If you opt to use olive oil, note that whatever prominent flavors you detect in the oil will also come through in the final brownie so use one that you like the flavor of. I don’t recommend using coconut oil.

Unsweetened cocoa powder – I tend to prefer Dutch-processed cocoa in this brownie recipe, as it tastes more chocolatey and has a less bitter flavor than conventional cocoa powder. That said, you’re welcome to use unsweetened natural cocoa powder.

Baking soda – for leavening, not to be confused with baking powder. If it’s been a minute since you used it, test for freshness by adding a small spoonful to a shallow bowl. Add a splash of the acid of your choice (e.g., white vinegar). If it fizzes and bubbles, it’s still good for baking!

Shredded Zucchini – this recipe will work well with nearly any kind of summer squash you throw at it. Zucchini is preferred, but yellow summer squash or patty pan squash can be substituted. They are essentially all the same; they just come in different colors and shapes.

Semi-sweet chocolate chips – I think semi-sweet is the perfect chocolate here, but feel free to swap in milk, dark, or even white chocolate chips if you’d like. Alternatively, you can use chopped bar chocolate. Just note that it won’t hold its shape as well as chips, so your brownies will be spotted with puddles of gooey chocolate instead of studded uniformly- both are delicious!

Butter & milk – these fudgy brownies with zucchini deserve an equally fudgy frosting. Feel free to swap in your favorite plant-based alternatives to make them vegan.

How To Make Zucchini Brownies

Set of two photos showing oil added to sugar and then cocoa powder poured into the bowl.

1. Preheat oven to 350°F. Grease a 9×13-inch baking pan with baking spray, and line it with parchment paper, letting excess hang over the sides. In a large mixing bowl, whisk together the wet ingredients (vanilla extract, oil, and sugar).

2. Add the dry ingredients (flour, cocoa, baking soda, and salt) to the large bowl.

Set of two photos showing the mixture stirred and shredded zucchini added.

3. Gently stir the mixture together with a spatula. (The batter will be dry at this stage.)

4. Fold in the grated zucchini until fully combined and the batter loosens up a bit.

Set of two photos showing chocolate chips folded into batter and spread into a baking pan.

5. Stir in chocolate chips.

6. Spread the brownie batter into an even layer in the prepared pan. Bake for 20 to 25 minutes or until a wooden pick inserted into the center comes out with a few moist crumbs. Let the brownies cool completely in the pan.

Set of two photos showing frosting whisked together and spread over the baked brownie slab.

7. While the brownies cool, make your frosting. In a medium bowl, whisk together the powdered sugar and cocoa powder. Add the milk and melted butter and whisk until smooth.

8. Remove the cooled brownies from the pan, and spread the frosting over the top. Let stand for 10 to 15 minutes to set up before slicing.

Overhead view of a slab of zucchini brownies on a lined cutting board with five pieces cut.

Pro Tips For Making This Recipe

Prep for easy cleanup. Parchment paper is your friend here, so don’t skip lining the pan. You should have a good overhang on all sides of the pan for the easiest, most seamless removal of the brownies possible. If you’re using a roll and the paper won’t stay flat, crumple it into a ball, then flatten it out — it should hold its shape much better.
No baking spray? No problem. While I love the convenience of having a non-stick spray with flour built right in, you can use other oils for this recipe. Feel free to use a paper towel or pastry brush and a small bowl of neutral oil to paint the inside of your pan with a thin coat. The oil in this recipe is mainly to keep the parchment paper in place and prevent the batter from baking onto the pan if any seeps through a cut in the paper.
Use your food processor for easy prep. While I typically use a box grater to shred zucchini, you can easily pull in a little electrical assistance. Use the grating blade with the large holes for the perfect consistency in seconds.

A forkful of zucchini brownie on a plate beside the rest of the brownie.

Frequently Asked Questions

Are these healthy brownies?

Defining them as healthy zucchini brownies might be up to you! I’d definitely consider these “better-for-you” than regular brownies. At the very least, you’re getting some good fiber and nutrients from the zucchini alongside the more decadent parts.

Do they need to be refrigerated?

For longer-term storage, yes. After cooling and frosting, place any leftovers in an airtight container. They’ll keep at a cool room temperature (around 68F) for 3 days, or in the fridge for up to a week.

Can they be frozen?

Absolutely! That said, I recommend holding off on adding the frosting if you have the choice. (If not, no worries. It’ll just be a bit messier once defrosted.) Allow the zucchini brownies to cool completely, then wrap well with several layers of parchment paper or plastic wrap to ward off freezer burn. They should keep well for up to 6 weeks. To use, defrost overnight in the fridge, then frost with chocolate icing before serving.

If you love this recipe try these out!

If you’ve tried this Zucchini Brownies recipe, then don’t forget to rate the recipe and let me know how you got on in the comments below, I love hearing from you!