Before starting, line a baking sheet with aluminum foil, waxed paper, or parchment paper.
In a large bowl, combine oats and rice cereal. Stir until combined.
In a microwave safe bowl, combine butter, brown sugar, honey, and vanilla.
Microwave for 30 second increments, until melted together.
Pour liquid mixture into oat mixture and still until combined.
Pour all of mixture into lined baking sheet. Press down and in until compacted into a rectangle. (To avoid sticking on your hands, you may want to "grease" them with a little bit of butter.)
If using chocolate chips, sprinkle on top and lightly press down.
Place in fridge for about 15 minutes, or until cooled and set. (Don't leave for TOO long or they will become very hard and may be difficult to cut.)
Remove from fridge and cut bars with a sharp knife or flat-edge pastry cutter.