Heat corn syrup and brown sugar in a saucepan, stirring until the sugar is dissolved. Remove from heat. Stir in the peanut butter until smooth.
Add in cornflakes and Cheerios. Stir to coat cereal well.
Press into 23x33cm/9x13” pan.
These bars can easily be frozen in an airtight container until ready to serve.
*Cheerios can be substituted for any toasted oat cereal.