Preheat oven to 350? F. Beat butter, powdered sugar and the vanilla in a large bowl with electric mixer on medium speed until light and fluffy. Gradually add flour and pecan, beating on low speed after each addition until well blended.
Shape dough into 1-inch balls. Place on ungreased baking sheets. (they do not spread during the cooking process, no need to leave extra room between the cookies on the baking sheet)
Bake 14 to 15 min. or until bottoms of cookies are lightly browned. Cool 5 min. on baking sheets. Roll warm cookies in powdered sugar until evenly coated; place on wire racks. Cool completely. Store in tightly covered container at room temperature.