Finely grate the zucchini using the small holes of a box grater. Place the grated zucchini on a clean kitchen towel or several layers of paper towels and gently squeeze to remove excess moisture. It should be damp but not dripping.
1 1/4 cups zucchini
Preheat the oven to 350°F (175°C). Line two baking sheets with parchment paper or silicone baking mats.
In a medium bowl, whisk together the flour, oats, baking soda, baking powder, salt, cinnamon, nutmeg, and optional ground ginger until evenly combined.
1 3/4 cups all-purpose flour, 1 cup old-fashioned rolled oats, 1 teaspoon baking soda, 1/2 teaspoon baking powder, 1/2 teaspoon fine sea salt, 1 1/2 teaspoons ground cinnamon, 1/4 teaspoon ground nutmeg, 1/4 teaspoon ground ginger
In a large mixing bowl, beat the softened butter, brown sugar, and granulated sugar with a hand mixer or stand mixer on medium speed for 2–3 minutes, until light and fluffy. Scrape down the bowl as needed.
1/2 cup unsalted butter, 3/4 cup light brown sugar, 1/4 cup granulated sugar
Add the egg and vanilla extract to the creamed mixture and beat on medium speed for 30–45 seconds, just until combined. If using Greek yogurt, mix it in on low speed until incorporated.
1 large egg, 2 teaspoons pure vanilla extract, 2 tablespoons plain Greek yogurt
Stir the grated, squeezed zucchini into the wet mixture on low speed or with a spatula until evenly distributed. The batter may look slightly curdled at this stage; this is normal.
1 1/4 cups zucchini
Add the dry ingredient mixture to the wet ingredients in two additions, mixing on low speed or folding with a spatula just until no dry streaks of flour remain. Do not overmix. The dough will be soft and thicker than muffin batter but looser than classic cookie dough.
1 3/4 cups all-purpose flour, 1 cup old-fashioned rolled oats, 1 teaspoon baking soda, 1/2 teaspoon baking powder, 1/2 teaspoon fine sea salt, 1 1/2 teaspoons ground cinnamon, 1/4 teaspoon ground nutmeg, 1/4 teaspoon ground ginger
Gently fold in your desired mix-ins, such as chocolate chips, nuts, raisins, dried cranberries, or shredded coconut, until evenly distributed.
1/2–3/4 cup semisweet chocolate chips, 1/2 cup chopped walnuts or pecans, 1/2 cup raisins or dried cranberries, 2 tablespoons shredded coconut
Using a 1 1/2-tablespoon cookie scoop or a rounded tablespoon, portion the dough onto the prepared baking sheets, leaving about 2 inches between each cookie. For a neater shape, gently press and round the tops with damp fingers. Optional: chill the scooped dough for 20–30 minutes for puffier cookies.
Bake one sheet at a time for 11–13 minutes, or until the edges are set and the tops look just dry in the center. The cookies will not brown deeply, so rely on texture rather than color. Rotate the pan halfway through baking if your oven bakes unevenly.
Allow the cookies to cool on the baking sheet for 5 minutes, then transfer them to a wire rack to cool completely. They will firm up as they cool but remain soft and cake-like.