Cover a large baking sheet with wax paper.
Spread the broken cookies, pretzels, peppermint chips, and about ¾ of the M&M's onto the baking sheet.
Place the white chocolate in a microwave-safe container and microwave for 1½ minutes on medium power. Stir and then microwave for another minute until melted and smooth.
Pour the melted chocolate over the cookie/candy mixture, spreading with a spatula if needed to coat completely.
Sprinkle the rest of the M&M's and red and green sprinkles over the still-wet chocolate.
Chill the tray of bark until set and firm, about 1 hour.
Remove and gently break bark into small pieces.