In a large iron skillet, melt margarine on medium heat. Add sugar, milk, and cocoa. Stir constantly until mixture begins to boil. Boil for exactly 1 1/2 minutes without stirring. Remove from heat and add peanut butter. Stir in completely and then stir in the oatmeal one cup at a time. When thoroughly mixed, drop by teaspoonful onto waxed paper or clean dry surface. Set up time is appoximately 5 minutes.