Pour Chex cereal in a large bowl then set it aside.
In a microwave safe bowl, add Chocolate Chips and Peanut Butter. Microwave on high for 45 seconds; stir. If mixture is not smooth, microwave it an additional 15 seconds then mix again. Add Vanilla and stir.
Pour chocolate mixture over Chex cereal, gently fold with a large spoon until all of the cereal covered. Next, pour it into a gallon size Hefty® Slider Bag.
Top the cereal with powdered sugar, slide the bag closed then shake it until the cereal is covered in powdered sugar. Next add the M&Ms and Reese's Pieces then shake the bag again.
Spread Halloween Monster Munch Muddy Buddies mix onto a cookie sheet covered in waxed paper to cool. Store Halloween Monster Munch in a Hefty® Slider Bag.