Preheat oven to 350°F. Using an electric mixer cream butter and sugars until light and fluffy. Add the eggs, vanilla and salt and beat well. In a large bowl, combine baking powder, baking soda, flour and oats. Stir to combine. Add this mixture to the butter mixture and stir until the dough comes together, then add the chocolate chips, coconut and walnuts and stir again until chips, coconut and walnuts are well integrated throughout the dough. Line four cookie sheets with parchment paper and scoop out the dough, 12 balls per cookie sheet. Each ball of dough should be about 4 tablespoons. Press the top of each ball of dough gently with the back of a spoon. Bake for 10-12 minutes or until lightly browned on top. Transfer to wire cooling racks. When cool, the cookies will be crunchy on the outside and delightfully chewy on the inside.