In a mixing bowl, cream butter and sugar. Add eggs and vanilla; mix well. Combine flour, baking powder, baking soda and oats; gradually add to creamed mixture and mix well. Stir in chips and 1 cup pistachios. Shape into 1" balls; place 2" apart on ungreased baking sheets. Lightly press remaining pistachios into cookies. Bake at 350 degrees for 10-12 minutes or until lightly browned. Cool 2 minutes before removing to wire