Heat oven to 350 degrees F and line a 8x8 or 9x9 pan with parchment paper, set aside.
Lightly processor the cereal in a food processor for about 30 seconds (this step is not mandatory but recommended for denser bars). In a large mixing bowl, mix the cereal, condensed milk, and melted butter until well combine.
Pour the mixture into the lined baking pan and press firmly and evenly over the entire surface. Bake for 20-30 minutes, 20 minutes for chewy and soft bars, 25 minutes for lightly crunchy bars, and 30 minutes for really crunchy bars. Remove from oven and allow to cool for 5 minutes, cut into 10-12 bars.
Bars can be stored at room temperature for up to 2 weeks in plastic wrap or an air tight container.