Collins Square is found a very short walk on the Collins Street side of Southern Cross Station. Its entrance is rather deceiving, as it's in between two office blocks. There is also a tram stop a few steps from Collins Square, where at least 2 trams go by to other ends of the city and other suburbs.
Collins Square Tower Four and Five 737 Collins Street Melbourne
Collins Square has a food court with numerous food shops including Bon Bon; Tahini; Ena; Belle's Hot Chicken; ThinkAsia and many others. It also has a pharmacist, Woolworths and it gives ground access to the Australian Passport Office, KPMG and other major companies.
For after-work drinks, you can go to Mr Collins or Bar Nacional on the street level.