Stir together 1 cup peanut butter, 1 cup sugar, 1 large egg, and 1 tsp. vanilla extract in a large bowluntil combined; shape dough into 1-inch balls. Place balls 1 inch apart on ungreased baking sheets, and flatten gently with tines of a fork. Bake at 325° for 15 minutes or until golden brown. Remove to wire racks to cool.