Pulverize the oats in the processor or blender until fine. Add the flour, baking soda, and salt and pulse to combine; set aside.
Cut the butter into chunks and melt in a large saucepan over medium heat. Remove from the heat and stir in the granulated sugar, brown sugar, and vanilla. Whisk in the egg. Stir in the flour mixture just until all of the dry ingredients are moistened. Let the mixture cool for a few minutes if it is at all warm. Stir in the nuts and chocolate chips. Cover and refrigerate overnight.
Preheat the oven to 325°. Position the racks in the upper and lower thirds of the oven. Line cookie sheets with parchment paper.
Remove the dough from the refrigerator to soften. Scoop rounded tablespoons of dough and place about 2-inches apart on the cookie sheets. Bake for 13- 15 minutes, or until the cookies are deep golden brown. Rotate cookie sheets from top to bottom and front to back about halfway through baking time to ensure even baking. Use a metal pancake turner to transfer cookies to racks to cool completely before storing or stacking.
May be stored, airtight, for several days.
Equipment:.Food Processor or blender & 2 cookie sheets, ungreased or foil lined.