Preheat oven to 350°F (175°C) and line a baking sheet with parchment paper.
Mix melted butter, brown sugar, and white sugar in a large bowl until smooth.
Add egg, pumpkin puree, and vanilla extract and mix well.
Stir in flour, oats, baking soda, cinnamon, nutmeg, and salt until a soft dough forms.
Fold in chocolate chips if using.
Scoop tablespoon-sized portions of dough onto the prepared baking sheet.
Bake for 10–12 minutes until edges are set and centers remain soft.
Let cookies cool on the baking sheet for a few minutes before serving.