Chocolate Peanut Butter Fudge

Butter one 9x9 inch pan.
Combine the sugar, evaporated milk and cocoa in saucepan. Stir over high heat until mixture comes to a rolling boil. Lower heat to medium and continue cooking to a soft ball stage.
Remove from heat, add peanut butter and margarine. Beat by hand until creamy; pour into prepared pan. Allow to cool and cut into squares.