Instant oatmeal has a long shelf life, but does eventually expire. Unopened or opened instant oatmeal can be stored in the pantry for 1 to 2 years past the printed date.
Flavored instant oatmeal has a shelf life of 6 to 9 months after the printed date. To maximize shelf life, oatmeal should be stored in airtight containers once opened.
Steel cut oatmeal can be safely stored for 2 to 3 years at room temperature. Oatmeal should be kept in a cool and dry location.
If oatmeal changes drastically in color, develops a foul odor or odd texture, it should be discarded. These are indications that it may be spoiled.