In the bowl of a stand mixer, cream butter and sugars together. Add in peanut butter.
Add oats, milk and vanilla, and mix briefly. Gently stir in chocolate chunks and M&Ms until thoroughly mixed.
Roll into 1 inch balls and place in mini muffin cups lined with papers.
Refrigerate balls at least 1 hour or until firm.
Melt chocolate coating in microwave or on stovetop. Using a fork, dip balls into chocolate. Tap fork against rim of bowl to shake off excess chocolate.
Place on foil lined baking sheet to harden. Refrigerate if needed. Once hard, place back in mini muffin paper cups to serve.