Preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper to prevent sticking.

In a large bowl, whisk together the oats, flour, baking powder, baking soda, cinnamon, nutmeg, and salt until well combined.

In a separate bowl, combine the melted butter, pumpkin puree, granulated sugar, molasses, and vanilla extract. Beat until smooth, then add the eggs one at a time, mixing well after each addition.

Pour the wet ingredients into the dry mixture and stir just until combined. The dough will be thick and a little sticky.

Scoop rounded tablespoons of dough onto the prepared baking sheets, spacing them about 2 inches apart.

Flatten each cookie slightly with the back of a spoon or your fingers.

Bake for 15-18 minutes, until the edges are golden brown but the centers still feel slightly soft.

Allow the cookies to rest on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.