Preheat oven to 350 F.
Cream together the peanut butter and vegetable oil in a bowl. Add brown sugar, vanilla, and egg. Beat well.
Add flour (reserve 1/4 1/2 cup) and baking soda. Blend thoroughly. Add enough extra flour so that you can shape dough into balls, slightly larger than 1-inch. Press a Peanut Butter Cup into each ball, covering the cup completely, and place on an ungreased baking sheet.
Flatten with a fork, bake about 10 15 minutes or until lightly browned.