Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper.

In a mixing bowl, cream together the softened butter, brown sugar, and granulated sugar until light and fluffy.

Add the pumpkin puree, egg, and vanilla extract to the mixture and mix until well combined.

In another bowl, whisk together the flour, oats, baking powder, baking soda, salt, cinnamon, and nutmeg.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined.

Fold in the chocolate chips and/or raisins if using.

Using a cookie scoop, drop rounded tablespoons of dough onto the prepared baking sheet.

Bake in the preheated oven for 10-12 minutes, or until the edges are lightly golden.

Allow the cookies to cool on the baking sheet for a few minutes before transferring to a wire rack to cool completely.