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These zucchini brownies are thick, deeply chocolatey, soft in the middle, and topped with a proper fudgy frosting. The undrained grated zucchini disappears into the batter, adding moisture and tenderness without taking over the flavor. You’re going to love how rich they are—and how good they stay the next day.
Why You’ll Love It
- Deep chocolate flavor — dark cocoa powder and dark chocolate chips make these brownies rich and intense.
- Extra-fudgy texture — undrained grated zucchini adds the moisture that keeps the centers soft.
- Proper chocolate frosting — the fudgy topping takes these from a simple treat to a full dessert.
- Great use for zucchini — finely grated zucchini disappears into the batter without changing the chocolate flavor.
Ingredient Notes
Use dark cocoa powder if you can. Hershey’s Special Dark is easy to find and works beautifully, with that deeper almost-black brownie color. Semi-sweet cocoa will work in a pinch, but the dark cocoa is more dramatic. And I like drama in a brownie, not in the family group chat.
The zucchini should be finely grated, skin and all, and you do not drain it. Wash and dry the zucchini before grating, naturally. I use the fine side of my old box grater—the one that has taken a little skin off more than once because apparently I cannot learn patience.
Sour cream may seem like an odd addition, but it gives these brownies a soft, moist texture and a bit of tang against all that sugar. Full-fat is what I generally have around, though I’m not going to send the zucchini police after you if you use what’s in your refrigerator.
For the chocolate chips, dark chips are my favorite. Semi-sweet will still be delicious. Pecans work well sometimes, but I prefer the little pockets of melted chocolate. This is one of those rare areas where I am firm. Until I change my mind later.
Ingredients
- 1 1/4 cups all-purpose flour
- 1 cup granulated sugar
- 3/4 cup dark cocoa powder, plus more for the frosting
- 1 teaspoon baking powder
- 1/2 teaspoon salt
- 1 cup dark chocolate chips
- 1/4 cup vegetable oil
- 2 teaspoons vanilla extract
- 1/4 cup sour cream
- 2 cups finely grated zucchini, undrained—about 1 good-sized zucchini, maybe two smaller ones
- 2 large eggs
For the chocolate frosting:
- 3 tablespoons melted butter
- 1/4 cup cocoa powder
- 3 tablespoons milk
- 3 cups powdered sugar
- 1 teaspoon vanilla extract
- A pinch of salt, just a pinch between your fingers
Instructions
Heat your oven to 350°F. Grease and flour a 9-by-9-inch baking pan, or line it with parchment paper if you are smarter than I am and enjoy lifting brownies neatly from a pan. I usually use parchment now, after scraping one too many corners with a butter knife and muttering things that would not be appreciated.
In a large bowl, stir together the flour, granulated sugar, dark cocoa powder, baking powder, salt, and dark chocolate chips. Break up any stubborn cocoa lumps with the back of your spoon. They are not dangerous, obviously, but biting into a dry cocoa clump is a disappointment of the highest order.
In another bowl, lightly beat the eggs. Add the vegetable oil, vanilla, sour cream, and finely grated zucchini. Mix it all together well. It will look a little strange—wet and green-flecked and not remotely like brownies yet. Stay with me.
Add the zucchini mixture to the dry ingredients and stir until everything is just combined. The batter will seem dry at first. Very dry, actually. The first time I made it, I was convinced I had forgotten something and nearly added milk. Don’t. Put down the milk.
Let the batter sit for 5 minutes. This is when the zucchini gives up its moisture and saves the day. After 5 minutes, stir it again. It should be noticeably wetter and easier to spread. If your zucchini was unusually watery, it may look a bit looser, but that’s okay. Zucchini has moods.
Spread the batter evenly in your prepared 9-by-9 pan. Bake for 35 to 45 minutes. Start checking around the 35-minute mark. A toothpick inserted in the center should come out with moist Crumbs—not wet batter, but not bone dry either. Overbaked brownies are sad little Cakes, and we are not making cake today.
Let the brownies cool completely in the pan. Completely. I know, I know. This is the part where impatience sets in. Frosting warm brownies gives you a chocolate landslide, which can be delicious but is not the assignment.
While the brownies cool, make the frosting. Whisk together the melted butter, cocoa powder, milk, powdered sugar, vanilla, and pinch of salt until smooth and creamy. If it seems too thick to spread, add a tiny bit more milk. If it gets too loose, add a little more powdered sugar. I say “tiny” because I once dumped in a splash of milk while distracted, and suddenly I had chocolate glaze instead of frosting. Still edible. Not pretty.
Spread the frosting over the cooled brownies. Let it set before slicing. If you want very clean squares, chill the frosted pan for about 30 minutes first. I rarely do this because I am not running a bakery, but it does make a nicer-looking plate.
Variations
Pecans can be swapped for the dark chocolate chips, and that version has a nice old-fashioned feel. You can use semi-sweet chocolate chips instead of dark if that’s what you have. Yellow squash can stand in for zucchini, too, though it can be a little different in moisture and texture.
I tried adding cinnamon because I had been making zucchini Bread and apparently lost track of who I was. It wasn’t terrible, but it tasted confused. Chocolate and zucchini need no help here. Let them do their thing.
If you prefer thinner brownies, you can bake the batter in a 9-by-13-inch pan. Start checking them about 10 minutes earlier, since they’ll bake faster. I like the thick 9-by-9 version best, though. I’m not saying thicker brownies solve life’s problems, but they certainly don’t make things worse.
Storage & Reheating
Keep the frosted brownies in an airtight container at room temperature for up to 3 days. They’ll also keep in the refrigerator for up to a week, though the frosting firms up when it’s cold. Let a square sit on the counter for a little while before eating, or warm it just briefly if you like it soft and fudgy.
For freezing, wrap individual brownies tightly in plastic wrap or foil, then tuck them into an airtight container. They thaw overnight in the refrigerator or in a couple of hours on the counter. I have been known to eat one half-frozen while unloading groceries in hot weather. Not proud, exactly. But it was hot, and the ice cream had melted, so.
Final Notes
There’s something satisfying about making a dessert from the zucchini nobody knows what to do with. Not virtuous—let’s not get carried away, there are three cups of powdered sugar in the frosting—but satisfying. Useful. A little sneaky, maybe.
A zucchini on the counter looks different somehow.
Anyway. Make the brownies. Don’t squeeze the zucchini. Don’t overbake them. And if the zucchini stays a secret until after two squares disappear, well… that is entirely up to you.
Zucchini Brownies
Ingredients
- 1 1/4 cups all-purpose flour
- 1 cup granulated sugar
- 3/4 cup dark cocoa powder
- 1 teaspoon baking powder
- 1/2 teaspoon salt
- 1 cup dark chocolate chips
- 1/4 cup vegetable oil
- 2 teaspoons vanilla extract
- 1/4 cup sour cream
- 2 cups zucchini finely grated and undrained, about 1 good-sized zucchini or 2 smaller ones
- 2 large eggs
- 3 tablespoons butter melted
- 1/4 cup cocoa powder
- 3 tablespoons milk plus a tiny bit more if needed
- 3 cups powdered sugar plus a little more if needed
- 1 teaspoon vanilla extract
- 1 pinch salt
Instructions
- Heat the oven to 350°F and grease and flour a 9-by-9-inch baking pan, or line it with parchment paper for easier lifting.
- In a large bowl, stir together the flour, granulated sugar, dark cocoa powder, baking powder, salt, and dark chocolate chips, breaking up any cocoa lumps with the back of a spoon.
- In another bowl, lightly beat the eggs, then add the vegetable oil, vanilla extract, sour cream, and finely grated undrained zucchini and mix well.
- Add the zucchini mixture to the dry ingredients and stir until just combined; the batter will seem very dry at first, so do not add milk.
- Let the batter sit for 5 minutes so the zucchini releases moisture, then stir again until it is noticeably wetter and easier to spread.
- Spread the batter evenly in the prepared 9-by-9-inch pan and bake for 35 to 45 minutes, starting to check around 35 minutes, until a toothpick inserted in the center comes out with moist crumbs but not wet batter.
- Let the brownies cool completely in the pan before frosting so the frosting does not melt into a chocolate landslide.
- While the brownies cool, whisk together the melted butter, cocoa powder, milk, powdered sugar, vanilla extract, and pinch of salt until smooth and creamy, adding a tiny bit more milk if too thick or a little powdered sugar if too loose.
- Spread the frosting over the cooled brownies and let it set before slicing; for very clean squares, chill the frosted pan for about 30 minutes first.