Cream the butter and brown sugar in a mixing bowl until light and fluffy.
Stir in the eggs, vanilla, flour, baking soda, salt and oats in the order listed.
Mixture will be quite thick.
Pat 2/3 of the oats mixture in a greased 10x15 inch cake pan.
Spread Chocolate Filling over the oats layer.
Sprinkle with the remaining oats mixture.
Bake at 350 degrees for 25 to 30 minutes.
Cool and cut into bars