Cream margarine, brown sugar and white sugar. Add Karo syrup, vanilla, baking soda and eggs; mix well. Beat in peanut butter. Pour over chocolate chips, M&Ms, walnuts and oatmeal. Mix together (I use my hand) .
Bake at 350 degrees for 10 to 12 minutes, depending on size of cookies. Let set 5 minutes before removing from cookie sheet to wire rack to finish cooling.
Makes such a large batch that I store some dough in large covered tupperware container and bake some a few days later. Can be frozen.