^ âeucatastropheâ (US) / âeucatastropheâ (UK) in Oxford Dictionaries, Oxford University Press.
A: Chopped or sliced onions can be stored in a sealed container in your refrigerator at the proper temperature of 40Â°F or below for 7 to 10 days (Source: USDA). For pre-cut fresh or frozen products, always use and follow manufactures use by dates.
Cut onions will be OK for a couple days in the fridge. If you are going to use it in cooking, chop the remainder of the onion when you first cut it up. Put it into a containerâ¦ and freeze. Then, you can take out what you need as you need it.   Another answer If kept in an airtight container 7 days.