Preheat your oven to 350°F (175°C). This ensures the cookies bake evenly and helps them rise properly.

In a large mixing bowl, cream together the softened butter, brown sugar, and granulated sugar using an electric mixer on medium speed until light and fluffy, about 2-3 minutes. This process incorporates air into the mixture, resulting in a lighter cookie.

Add the pumpkin puree, egg, and vanilla extract to the butter-sugar mixture. Mix until well combined, scraping down the sides of the bowl as needed.

In a separate bowl, whisk together the oats, flour, baking soda, baking powder, cinnamon, nutmeg, and salt. This helps to evenly distribute the dry ingredients and ensures no clumps remain.

Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined. Be careful not to overmix, as this can lead to tough cookies.

Fold in the chocolate chips using a spatula, ensuring they are evenly distributed throughout the dough.

Line a baking sheet with parchment paper to prevent sticking and make cleanup easier.

Using a cookie scoop or tablespoon, drop rounded balls of dough onto the prepared baking sheet, spacing them about 2 inches apart to allow for spreading during baking.

Bake in the preheated oven for 10-12 minutes, or until the edges are lightly golden. The centers may look slightly underbaked, but they will continue to cook on the baking sheet after being removed from the oven.

Allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely. This helps them set and maintain their chewy texture.