Line your metal muffin pan with paper liners or use a silicone muffin pan without the need for liners.
Start with the oat layer. Mix quick-cooking oats, honey, peanut butter, and mini chocolate chips in a bowl. If it feels dry, add 1 to 2 teaspoons of water. Press about 2 tablespoons of the oats into each muffin cup.
Proceed with the chocolate layer. Melt dark chocolate and coconut oil in a microwave-safe bowl, stirring at 20-second intervals. Spoon 2 teaspoons of melted chocolate onto the oat layer, swirling the pan for even distribution. Freeze for 5 minutes.
Now, the peanut butter layer. Microwave peanut butter and coconut oil for 15 seconds, stir until well combined. Add 2 teaspoons of the peanut butter mixture on top of the chocolate layer, swirl to even it out. Sprinkle mini M&Ms and mini chocolate chips on each cup.
Freeze the muffin tin for at least 30 minutes to an hour to set.
Once set, transfer the oat cups from the muffin pan to a freezer bag and store in the freezer.