In a large microwaveable bowl, combine the sugar, butter and evaporated milk. Cook on high power for 2 to 5 minutes, stirring occasionally until the mixture comes to a rapid boil. Allow the mixture to boil undisturbed for 20 to 30 seconds. Remove from heat and stir in the instant pudding and oatmeal. Spoon onto greaseproof paper lined baking trays. Allow to sit at least 15 minutes or until firm.