Preheat oven to 350 degrees. Combine dry ingredients flour, baking powder, baking soda, salt and set aside. In a large bowl cream softened butter, sugar, dark brown sugar, eggs and vanilla until light and fluffy. Add about 1/3 of your dry ingredients and mix just until flour is no longer visisble. Then repeat until all flour mixture has been added. Stir in oatmeal, chips and walnuts.
Using a cookie scoop drop onto ungreased cookie sheet about 2 inches apart. Bake for 11-12 minutes. Let cool on sheet for a couple of minutes before transferring them to cooling rack. Enjoy!