Sift flour, baking powder, baking soda and salt in a medium bowl; set aside.

With an electric mixer, beat butter and sugars at medium speed 3 minutes or until light and fluffy. Turn mixer to low and add egg and vanilla, mixing just until combined. Add oats and peanut butter, mixing gently.  Add sifted ingredients in three batches and mix each batch only until just incorporated, scarping down sides of mixer after each time (do not over mix). Stir in chocolate chips, raisins and walnuts, just until combined.

Using a tablespoon cookie scoop, drop cookies 2 inches apart on prepared cookie sheet. Gently press down with a fork or back of a spoon. Bake 18 minutes or until edges are browned. Remove to a wire rack and let cool. Store an airtight container.