Line an 8x8 inch pan with parchment paper and set aside.
In a large bowl, stir together oats, Rice Krispies, pretzels, and mini M&Ms. Set aside.
In a medium-sized saucepan, melt butter, honey, peanut butter, and brown sugar. Bring to a boil, then let simmer on medium-high heat for 2-3 minutes, stirring continuously. Remove from heat and stir in vanilla.
Pour mixture over dry ingredients and stir together until everything is well-combined.
Press mixture firmly and evenly into prepared pan, making sure to pack everything in nice and tight.
Refrigerate for 30 minutes.
Melt candy melts in microwave at 30 percent power for 30 seconds, repeating until melted. Pour melted chocolate into a pastry bag or use a fork to drizzle melted chocolate over the tops of the bars. While candy melts are still tacky, sprinkle on additional mini M&Ms.
Return to refrigerator until ready to cut and serve or package. Store in an airtight container.