Sourdough Discard Zucchini Bread

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This sourdough discard zucchini bread is tender, sweet, and subtly spiced. It’s one of the best ways to use up your fresh summer zucchini.

Slices of sourdough discard zucchini bread with a buttered knife the foreground

Table of Contents

This summer, our garden has been hit or miss, but zucchini is always a reliable harvest. I just planted another round, which means we have plenty to use up again.

Sure, you can sauté or grill zucchini. I even sneak it into my slow cooker lasagna. But my favorite way to use extra zucchini is in this easy sourdough zucchini bread.

And of course, I always have sourdough starter sitting around. So I like to use it up for zucchini bread and other summery discard recipes, such as strawberry shortcake, peach pie, and lemon bars.

When I told my four-year-old I made zucchini bread, she was unsure at first—until she took a bite. Then, she happily ate two slices and asked for more for breakfast the next day.

If you’ve made my sourdough apple cinnamon bread, the method will be familiar, and the result is just as delicious.

Whether your garden is overflowing or you’re simply looking for a new sourdough discard recipe, this zucchini bread with sourdough starter is one I make all summer long.

A loaf of sourdough discard zucchini bread on a wire rack with a fresh zucchini

Why You’ll Love This Recipe

Sourdough: This quick bread uses up that extra sourdough discard you have in the fridge. So there is no waste!

Summer Produce: I love anything that highlights summer produce. And this is one of the best ways to use up extra zucchini from the garden or farmers’ market.

Easy and Delicious: This sourdough discard quick bread is simple to make and every bit as delicious as it looks.

Versatile: Enjoy it for breakfast, as a snack, or even dessert.

Freezer-Friendly: If you have an abundance of zucchini, make two loaves and freeze one for later.

Ingredients

Zucchini: You will need a fresh zucchini for this recipe.

Sourdough Starter: Use active or inactive sourdough starter. If you have frozen starter, pull some out to thaw beforehand.

Flour: I used all-purpose flour for this recipe. If you want to swap all-purpose for fresh-milled flour, use soft white wheat and increase the amount by 1/4 cup.

Avocado Oil: I prefer avocado oil, but any neutral oil will work.

Get the full list of ingredients and measurements on the printable recipe card below.

Tools You Will Need

Stand Mixer: Use a stand mixer to mix the wet ingredients. I use a KitchenAid bowl-lift mixer and love it. A hand mixer will also work.

Loaf Pan: An 8″x4″ or 9″x5″ loaf pan will work for this recipe. I used a 9″x5″ stone loaf pan.

Step-by-Step Instructions

A close up of a zucchini and baking ingredients

Step 1: Gather the ingredients. Preheat the oven to 325° F and grease an 8″x4″ or 9″x5″ loaf pan (mine is a 9″x5″).

Sourdough zucchini bread dry ingredients in a mixing bowl, shown with a whisk

Step 2: In a medium mixing bowl, whisk together the all-purpose flour, salt, baking powder, baking soda, and cinnamon. Set aside.

A split image: the top showing the wet ingredients in a stand mixer bowl, the bottom showing them mixed together

Step 3: In the bowl of a stand mixer, add the starter, avocado oil, whole egg, egg yolk, sugar, and vanilla.

Mix on medium speed using the paddle attachment until the ingredients are well combined.

A split image: the top showing flour in the batter, the bottom showing it mixed together

Step 4: Add the flour mixture to the stand mixer bowl. Mix on low speed just until combined. Do not overmix. The batter will be thick.

Sourdough discard zucchini bread batter with shredded zucchini and walnuts on top

Step 5: Add the zucchini and walnuts. Use a spoon or spatula to fold them into the batter. Again, do not overmix.

A stone loaf pan filled with sourdough discard zucchini bread batter

Step 6: Spoon the batter into the prepared loaf pan. Bake for 60-65 minutes or until a toothpick inserted in the center comes out clean.

Baked sourdough discard zucchini bread cooling in a loaf pan and cooling on a wire rack

Step 7: Let the bread cool in the pan on a wire rack for an hour before serving.

Tips for Success

Don’t squeeze the liquid out of the zucchini. I know this is common in many recipes. However, this recipe relies on the water from the zucchini.
Use sourdough discard that has been fed within the last few days. If it’s been unfed for too long, it will taste acidic.
You can certainly serve this quick bread while it’s warm. However, it will slice and hold its shape better if it has cooled to room temperature.
Check for doneness with a toothpick. Zucchini adds a lot of moisture, and the bread can look done on top while still being underbaked inside. Extend the bake time by 5-minute increments until done.

A hand holding a slice of sourdough zucchini bread with a smear of butter and a bite taken out

Storing & Freezing

Counter: Store the cooled loaf in an airtight container for up to 3 days.

Fridge: Wrap in plastic or place in a sealed container and refrigerate for up to 1 week.

Freeze Whole Loaf: Wrap tightly in plastic wrap and foil, then freeze in a zip-top bag for up to 3 months.

Freeze Slices: Wrap individual slices, freeze flat, then transfer to a bag for easy grab-and-go portions.

To Thaw: Let thaw in the fridge overnight or warm slices in a toaster oven before serving.

Stacked sliced of sourdough zucchini bread with a buttered knife

Variations

Chocolate: Add cocoa powder and chocolate chips for a simple chocolate zucchini bread.

Muffins: Divide the batter into a muffin tin and bake at 350°F for 18 to 22 minutes (or until it passes the toothpick test)

Add-Ins: Fold in chopped pecans, raisins, or shredded coconut for extra texture and flavor. About ½ cup total works well.

FAQs

Can I make this without eggs?

I have not tested this recipe without eggs. But in most quick bread recipes, you can substitute the egg with two flax eggs (2 tablespoons ground flaxseed mixed with six tablespoons water). Keep in mind, this may make the texture slightly denser.

Can I bake this in a bundt pan?

Yes, you can. But check for doneness around 40 minutes and every 5 minutes thereafter.

Do I have to squeeze the zucchini?

No, not for this recipe. This recipe needs the water from the zucchini.

Can I reduce the sugar?

You can reduce the sugar by 1/4 cup without affecting the texture too much, but the loaf won’t be as sweet.

Close up of a slice of sourdough zucchini bread

Let’s Connect!

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