1/3 c. peanut butter
3 c. confectioners' sugar
1 1/2 tsp. vanilla
1/4 c. milk (up to 1/3 c. if needed)

Blend peanut butter and confectioners' sugar. Stir in vanilla and milk. Beat until frosting is smooth and of spreading consistency. Frosts one 9 x 13 inch pan.