Preheat oven to 350 degrees. Line a 9x13 inch metal pan with non-stick foil or parchment. If you'd rather, you can just grease it or spray it.
In a large mixing bowl, mix together oats, flour, brown sugar, salt (if using) and baking soda; stir in butter and mix until crumbly. Reserve 1 cup of the oatmeal mixture and put it in the refrigerator to chill.
Press remaining oatmeal mixture in pan.
Bake 10 minutes; cool for at least 5 minutes.
Prepare brownie batter. In a mixing bowl (I used the same one from the oatmeal), mix the brownie mix, oil, water and eggs and beat 50 strokes with a wooden spoon. Spread dough over baked layer. Crumble up chilled, reserved oatmeal mixture and sprinkle it over the top. Sprinkle on the chocolate chips.
Bake for 30 minutes or until top appears set. Cool completely. Chill if desired (It will give you a cleaner cut). Lift from pan, set on a cutting board and cut into 32 squares