Preheat your oven to 350°F (175°C). Line a baking sheet with parchment paper for easy cleanup.
In a large mixing bowl, cream together the softened butter, brown sugar, and granulated sugar until light and fluffy.
Mix in the canned pumpkin puree, egg, and vanilla extract until well combined.
In a separate bowl, whisk together the all-purpose flour, oats, baking soda, ground cinnamon, ground nutmeg, and salt.
Gradually add the dry ingredient mixture to the wet ingredients, stirring until just combined. If desired, fold in raisins or chocolate chips for added texture and flavor.
Use a cookie scoop or spoon to drop spoonfuls of cookie dough onto the prepared baking sheet. Leave some space between each cookie to allow for spreading.
Bake in the preheated oven for 10-12 minutes, or until the edges turn golden brown. The centers may look slightly undercooked, but they'll set as the cookies cool.
Remove the cookies from the oven and let them cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely.
