In a medium mixing bowl, combine the rolled oats, peanut butter, honey (or maple syrup), vanilla extract, and salt. Mix until well combined and the oats are fully coated.
If using, fold in the chocolate chips until evenly distributed.
Line a muffin tin with paper liners or lightly grease it.
Spoon the mixture into each muffin cup, pressing down firmly to pack it in.
Refrigerate the cups for at least 30 minutes to set.
Once set, remove the cups from the muffin tin and enjoy! Store any leftovers in an airtight container in the refrigerator.