Spread out a large piece of parchment paper out onto the counter or onto a baking sheet.
Toss together cereal, pretzels and M&Ms in a very large bowl.
In a double boiler, gently melt two bags of white chocolate chips, stirring frequently. You can also temper the chocolate in the microwave. Use the defrost setting to heat chocolate in a microwave safe bowl in 15-20 second intervals, stirring vigorously in between until just melted.
Using a wooden spoon or a spatula, drizzle melted white chocolate all over cereal, candy, pretzel mix and fold gently until everything is completely coated. Be gentle and try to avoid breaking up the cereal and pretzels as you mix.
Turn mixture out onto parchment and spread into an even later. Let harden for about 30-40 minutes.
Break up into chunks and store in an airtight container!
Reindeer feed stores in an airtight container at room temperature for about a week. Store feed in the freezer to have on hand all season!