In a medium-size microwave safe bowl, mix butter, white corn syrup and brown sugar. Place the mixture in the microwave and cook 2 minutes, or until butter melts.
Place the cereal, pretzels and peanuts into the prepared roasting pan. Pour the melted butter mixture over the cereal mix and mix gently until the cereal and nuts are coated.
Bake for 1 hour, stirring every 15 minutes.
Immediately spread out onto parchment paper to cool.