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, 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!