In a large saucepan, bring the brown sugar, butter and corn syrup to a boil over medium heat, stirring occasionally. Spread cereal in a large roasting pan. Pour syrup mixture over cereal and stir until well coated. Sprinkle with nuts and stir.
Bake at 250° for 1 hour, stirring every 15 minutes. Spread on waxed paper to cool. Break apart and store in airtight containers.