I found your blog while doing a search for a recipe for Lehi Roller Mills pecan pie bars. I thought I would respond to your request for a peanut butter bar. I don't know if this is comparable to the Lehi Roller Mills mix, but here is a recipe for peanut butter bars that my family enjoys.

PEANUT BUTTER FINGERS
3/4 C margarine
3/4 C brown sugar
3/4 C granulated sugar
3/4 C peanut butter
2 eggs
1/2 t salt
3/4 t baking soda
1/2 t vanilla
1 1/2 C flour
1 1/2 C oatmeal

Cream margarine, sugars, peanut butter, and vanilla . Add eggs and mix well. Add all dry ingredients except oatmeal. Mix well. Mix in oatmeal.

Spread in a 10x15 pan and bake at 350 degrees for 10-15 minutes until browned. Cool and frost. Cut into "fingers."

I frost it with a frosting made with margarine, cocoa, vanilla, powdered sugar, and milk. Sorry I don't have measurements...I just dump and mix.