Preheat the oven to 190°C/375°F/Gas mark 5
Sift together flour, baking powder, soda, and salt. Add the rolled oats, coconut, and nuts. Cream together the butter and sugar until fluffy; stir in vanilla and sour cream. Stir in the flour mixture gradually, making a stiff dough.
Drop by teaspoonfuls onto a lightly greased baking sheet. Bake for 12 to 15 minutes, or until lightly browned. Cool for a few minutes on the baking sheet before removing to a cooling rack.
