In the bowl of a stand mixer, or use a hand-held blender, combine the butter, cream cheese, and peanut butter. Cream together until light in color and combined.
Mix in the vanilla extract and brown sugar. Beat to combine.
Add the powdered sugar, quick oats, mini chocolate, chips, and 1/3 cup of the m&m's. Mix together until combined.
Use a spatula or your hands and form it into a ball. The dough is not sticky and will form easily. Place the cheeseball on the serving plate and gently press the remaining m&m's onto the top and sides.
Cover with plastic wrap and let refrigerate for 1-2 hours. You can also serve it right away too, but it will be soft. I like it best refrigerated. The dip is firm immediately from the fridge, but as it sits at room temperature it will soften it up making it easy to dip.
Serve with your favorite dippers; pretzels, nutter butter cookies, nilla wafers, etc.