Combine cereals, peanuts and pretzels in a large bowl and set aside.

Combine corn syrup, brown sugar and margarine in a medium saucepan and bring to a boil on medium heat; boil 3 minutes, stirring constantly.

Stir vanilla extract into sugar mixture after boiling is complete.

Immediately pour sugar mixture over cereal mixture, and stir well to coat.

Stir Mini M&M's into mixture.

Using a greased spatula, press mixture tightly into a greased 15X10" jellyroll pan (or cookie sheet) and cool at room temperature.

Cut into bars when completely cooled.