Place 3 baking sheets on a clear surface, like a table. Line each baking sheet with strips of parchment or wax paper.
In a large bowl, combine the Cheerios, corn Chex, peanuts, M&Ms and miniature pretzels. Set aside. Tip: Use two large bowls for easier mixing.
In a microwave, safe bowl, heat the chocolate chips and vegetable oil on medium high for 2 minutes, stirring once.
Microwave on high for 10 seconds at a time; stirring in between until smooth.
Pour over the cereal mixture. Mix very well, making sure to get the ingredients at the bottom of the bowl. The white chocolate cools quickly so move deliberately!
Spread cereal and white chocolate mixture onto the wax or parchment paper-lined baking sheets.
If desired, sprinkle powdered sugar over the cooling white chocolate chex mix.
Let the white chocolate harden.
Store in airtight container(s).