Preheat oven to 325°. Spray a 15x10xi-inch jelly roll pan.
In a large bowl, cream the butter, peanut butter and sugars until light and fluffy. Beat in the eggs and vanilla. Add the flour, oats, baking soda and salt and mix well
Spread into a prepared pan. Bake for 16-20 minutes or until they begin to turn golden on the edges (the center will still look under baked, don't over cook!).
In a microwave save bowl, melt chips and peanut butter for 1 minute, stir until smooth (if necessary, cook in additional 15 second increments until smooth). Pour over warm bars and spread evenly. Cool completely on a wire rack before cutting.