Preheat the oven to 375ºF. Line two baking sheets with parchment paper.
Add the oats to the bowl of a food processor and blend until they're a powder-like consistency.
In the bowl of a stand mixer fitted with the paddle attachment, cream together the butter, brown sugar and sugar.
Add the eggs one at a time, mixing after each addition, then add the vanilla.
Add the flour, salt, baking powder, baking soda and blended oatmeal and mix until combined.
Add the chocolate chips and nuts (optional), mixing to combine.
Shape 2 to 3 tablespoons of dough into mounds spaced 2 inches apart on the baking sheets.
Bake the cookies until the centers are barely set, 12 to 15 minutes. Remove the cookies from the oven and let them cool on the baking sheets for 5 minutes before transferring them to a rack to cool completely.