Pour cereal in a large mixing bowl. Next, prep a cookie sheet with parchment or wax paper, set aside.
Place chocolate chips, peanut butter, and butter in a large microwave safe bowl. Cook for 1 minute and stir. If it's not completely melted put it back in for up to 30 seconds more. Once it's melted, add vanilla and mix. Pour it over your Chex Cereal and mix with a spatula until well coated.
Take a large plastic Ziploc bag and place powdered sugar inside, then add chocolatey cereal. Close and begin to shake it up so that all the squares are evenly covered with sugar. Place the Reindeer Chow on the baking sheet and let it cool. Once you're ready to serve, add holiday M&MS or other season candy and chow down!!
Be careful not to over stir when adding the candy, it may crush the cereal.