Preheat your oven to 375°F (190°C) and line a baking sheet with parchment paper.
In a large mixing bowl, cream together the softened butter, granulated sugar, and brown sugar until light and fluffy.
Add the eggs one at a time, beating well after each addition. Stir in the vanilla extract.
In a separate bowl, combine the flour, rolled oats, baking powder, baking soda,and salt. Gradually add the dry ingredients to the butter-sugar mixture, mixing well after each addition.
Stir in the chocolate chips and chopped nuts until they are evenly distributed throughout the cookie dough.
Drop rounded tablespoons of dough onto the prepared baking sheet, spacing them about 2 inches apart. You can also use an ice cream scoop for uniform-sized cookies.
Bake in the preheated oven for 10-12 minutes, or until the edges are golden brown.
Remove the baking sheet from the oven and let the cookies cool on the sheet fora few minutes. Then transfer them to a wire rack to cool completely.
Enjoy your homemade Neiman Marcus chocolate chip cookies!