How to Store Onions – Onions should be kept in a dark, cool, dry area where there is good ventilation.  The refrigerator is too moist and they will spoil faster and often become soggy. A good place to store them is in the dark corner of the garage in a basket.  They should never be kept in plastic bags because they need good ventilation or stored with potatoes because of the ethylene gas potatoes release which promote rapid spoilage.