Lightly grease large cookie sheets; set aside.
In a large mixing bowl, beat the peanut butter and butter with an electric mixer on medium to high speed for 30 seconds. Add the packed brown sugar, granulated sugar, baking powder, and baking soda. Beat on medium speed until mixture is fluffy.
Add the eggs and the vanilla; beat until combined. Beat in the flour with the mixer on low speed. With a wooden spoon, stir in the rolled oats and the raisins and/or chocolate.
Using 1/4 cup dough for each cookie, drop the dough 3 inches apart on greased cookie sheets. Press the dough into 4-inch circles.
Bake the cookies in a 375° F oven for 10 to 12 minutes or until the edges are golden. Let the cookies stand for 1 minute on the cookie sheets. Transfer the cookies to wire racks to cool.