1/2 c. (1 stick) butter, softened
1/4 c. vegetable oil
1 1/2 c. powdered sugar
1 egg
2 c. all-purpose flour
1 tsp. baking soda
1 tsp. cream of tartar
1 tsp. vanilla extract

Combine first 4 ingredients, mixing well. Set aside.

Combine flour, baking soda and cream of tartar. Add to butter mixture, stirring until well blended. Stir in vanilla. Chill dough at least 1 hour. Shape dough into 1-inch balls. Place about 2-inches apart on ungreased cookie sheets.

Bake at 350°F for 10 to 12 minutes.