Spray a 9x13 baking dish with cooking spray or oil and set aside.

In a medium saucepan, add the butter and melt on medium heat.

Once the butter has melted, stir in the entire bag of marshmallows.

Once the consistency of the marshmallows is smooth and melted, remove and turn off the heat and immediately add the cereal 2 cups at a time, folding the cereal each time to coat evenly.

After all the cereal is mixed into the marshmallows, pour it into the 9x13 baking dish and press it into the baking dish with a baking spatula.

Allow to cool for at least 30 minutes, cut into squares and enjoy!