Preheat oven to 350 degrees. Prepare cookie sheets with cooking spray or parchment paper.
In a small mixing bowl, combine flour, baking powder, baking soda and salt. Set aside.
In a large mixing bowl, combine butter and sugar. Mix until creamy and light about 1 minute. Add in egg and vanilla. Beat until light and fluffy.
Stir in flour mixture. Mix well. Stir in oatmeal, coconut, raisins, and walnuts.
Drop by tablespoon-full or with a medium stainless steel scoop onto prepared cookie sheets. Bake for 10-12 minutes until golden brown. Cool on wire racks.