In small bowl, combine flour, baking powder, soda and salt.
In large bowl, beat margarine and peanut butter until well blended.
Beat in sugars until blended.
Beat in eggs and vanilla.
Add flour mixture and mix well.
Shape dough into 1-inch balls, (if dough is too soft to handle, cover and refrigerate 20 minutes or so.) Place 2 inches apart on ungreased cookie sheet. Using the back of a fork dipped in granulated sugar, flatten balls making crisscross pattern.