What's 500g onions? Usually around 3 large, or 4 medium. Sometimes our onions are teeny (depending at what time of the season) and so far more. British onions start in around July and August taking us right through 'til May, and until then - Spainish onions help us bridge the gap. Onions are a staple in most households and cuisines - and go in most dishes. We'd always recommend going big - they should last a while - especially our organic fresh onions. They don't sit in a warehouse for weeks in store!