Line a large sheet pan with parchment paper and set aside.
Add Chex, pretzels, Cap’n Crunch, Cheerios, and M&M’s to a very large bowl. Gently toss to combine.
Add white chocolate chips and oil to a medium microwave-safe bowl. Microwave for 30 seconds, stir, then microwave for 25 more seconds. Stir until smooth. If needed, microwave in 10-second bursts, stirring well between each burst, until fully melted.
Pour melted white chocolate over the snack mix, scraping every bit from the bowl with a spatula. Working very quickly, gently fold until the cereal mixture is evenly coated.
Transfer the coated mix to the prepared sheet pan and spread into an even layer. Immediately press a few extra M&M’s on top and add sprinkles, if using. Add these quickly before the white chocolate sets so they stick.
Let harden at room temperature, or place in the fridge until firm, about 10 to 20 minutes. Break into pieces and serve.
Video
Notes
Note 1: During the summer, many stores sell red, white, and blue M&M’s in the seasonal section. You can also find them online. In a pinch, use regular M&M’s and pull out the red and blue ones.Note 2: Sprinkles are optional, but they make the mix extra fun. I love star sprinkles or these sprinkles.Nutrition Note: Nutrition information is for about 1/2 cup per serving.Storage: Store in an airtight container at room temperature for up to 1 week. I like it best within 3 to 4 days. Freeze leftovers in an airtight container or bag for up to 3 months. Thaw at room temperature.