Preheat oven to 325 degree F. In a medium mixing bowl stir together flour and sugar. Using a pastry cutter, cut in margarine until mixture resembles fine crumbs and starts to cling. Stir in pistachios. Form mixture into ball. Knead just until smooth. Wrap dough. Chill for 1 hour or until easy to handle.
On a lightly floured surface roll the dough into a 10x6-inch rectangle. Cut the dough with decorative 2-inch cookie cutters or slice into thirty 2x1-inch strips. Place cut shapes or strips 1 inch apart on an ungreased cookie sheet.
Bake for 18 to 22 minutes or until bottoms are lightly browned. Cool on sheet 5 minutes. Transfer to wire rack; cool for 30 minutes.
In a medium mixing bowl combine powdered sugar, orange juice, and vanilla. Stir in additional juice, 1 teaspoon at a time, until the icing reaches piping consistency. If desired, tint a portion of the icing with food coloring. Decorate cookies as desired with icing. Store in a tightly covered container. Makes 30 cookies.