Although instant oatmeal has a lengthy shelf life, it does expire eventually. Instant oatmeal can be stored in the cupboard for 1 to 2 years after the printed date has passed.
The shelf life of flavoured instant oatmeal is 6 to 9 months after the printed date. Once opened, oats should be stored in sealed containers to extend its shelf life.
Steel cut oatmeal can be stored at room temperature for up to 3 years. Oatmeal should be stored in a cool, dry place.
If the colour of the oatmeal changes dramatically, it acquires a terrible odour, or it has an unusual texture, it should be discarded. These are signs that it may have been spoilt.