Most likely the same one reported by Aaron Clausen (how many other random onion orchids can there be in Barton?), but maybe with some closer photos, it can be confirmed as Microtis unifolia instead of the generic Microtis sp?
Yep exact same plant - what a cracking specimen isn't it? It's like perfectly healthy. I know of one other (smaller) onion growing in a nearby garden bed as well, but it's harder to find.
It's my first time seeing an onion orchid and it's does look great. It's actually much taller than I expected. I found a different group of potato orchids (maybe about 5 more) in another garden bed, but haven't seen any more onion orchids yet.
This is the other onion orchid, reported it today. Had to use the crappy zoom on my phone (very poor photo sorry), but couldn't be seen jumping in the garden beds in a work suit! http://canberra.naturemapr.org/Community/Sightings/Details/3384725
CludFED: This is the best onion orchid specimen I've EVER seen so you've seen a really perfect one I reckon for your first sighting. The ones up the bush are generally not quite as lush/perfect as this one.
You've got keen eyes to spot that second one, and I'm glad my first onion orchid was such a great specimen. It must really like whatever is in the ground in that garden bed.