In a heavy saucepan stir together sugar and cocoa powder. Stir in milk. Add margarine or butter and corn syrup. Bring to boiling, stirring occasionally. Boil vigorously for 3 minutes. Stir peanut butter into mixture in saucepan till smooth. Then stir in rolled oats till well combined. Return mixture to boiling. Remove from heat. Using a wooden spoon, beat mixture till slightly thickened. Immediately drop mixture from a rounded teaspoon on a waxed paper lined cookie sheet. If mixture spreads too much , beat it a little longer. Cool.