Preheat oven to 325º F (165º C). In a large bowl beat together butter, brown sugar, and white sugar. Add eggs and vanilla, and beat well. With a large spoon/spatula, mix in flour, baking soda, and salt until just barely mixed. Mix in oats, walnuts, and chocolate chips. Take heaping spoonfuls (about the size of golfballs) and place on an ungreased baking sheet. Bake for 15 min and you don't really want to wait for the cookies to brown. They will be perfectly chewy. Enjoy!