In a medium mixing bowl, combine the rolled oats, peanut butter, honey (or maple syrup), chocolate chips, salt, and vanilla extract. Stir until all ingredients are well mixed and form a sticky mixture.
Line a muffin tin with paper liners or lightly grease it.
Divide the mixture evenly among the muffin cups, pressing down firmly to pack it in.
Place the muffin tin in the refrigerator for at least 30 minutes to allow the cups to set.
Once set, remove the cups from the muffin tin and enjoy! Store any leftovers in an airtight container in the refrigerator.