To prepare raw onions for freezing, wash, peel and chop them into 1/2-inch pieces. Put the onions in freezer bags. Be sure to squeeze out all the excess air.
Lay the bags of onions flat on a cookie sheet and place it in the freezer until the onions are solid. Remove the pan, and stack the bags in the freezer. Onions stay fresh for three to six months after freezing.
Frozen onions do not need to be thawed before they are added to a recipe. If the entire bag is not needed, break off a chunk from the frozen mass. If necessary, run the bag under hot water to make separating some of the onions easier.