||Beat butter, shortening, and sugar at medium speed until creamy. Add vanilla and stir well.
In a separate bowl, combine flour, oats, salt, and 1/2 cup of chopped pistachios. Gradually add flour mixture to butter mixture. Mix well. Cover and refrigerate for an hour.
Preheat oven to 325°.
Roll cookie dough in 1-inch balls. Roll each ball in remaining chopped pistachios, coating well. Place balls about 2 inches apart on ungreased baking sheets. Bake about 15 minutes, or until edges are slightly browned. Cool on wire racks.
Makes about 3 dozen cookies.