In large mixer bowl, beat margarine and sugar until creamy. Add vanilla; then gradually beat in flour, blending thoroughly.
Gather dough into a ball, wrap tightly in plastic wrap, and refrigerate until firm (1 hour) or for up to 3 days.
Preheat oven to 300 degrees F (150 degrees C).
On lightly floured board, roll out dough to 1/4" thick. Cut, place on lightly greased sheets. Bake 35-40 minutes or until firm to the touch (press very lightly to test). Transfer to racks and let cool. Store in an airtight container.