OZ is undoubtedly one of the best places to do a long distance bike ride. You won't glide by quaint old castles or challenge yourself on 10,000 ft passes, but you will encounter a unique variety of wildlife and meet some of the friendliest folks in the world. Easiest riding (logistically) is along the east coast. Plenty of stores, tourists and pristine beaches.
Adventure cycling, though is riding along the edge
of the Outback. The towns are small, often defined only by the presence
of a pub and petrol station, but they're often only a days ride apart,
ideal for a cycle traveller. You can pedal west from Hay, New South Wales,
with the Murrumbidgee River on your left, and a thousand miles of red dirt
and dust on your right.
Or, you can cross the Nullabor Plain. Absolute serenity (with the exception
of a few trucks and road trains) for days. Just carry plenty of water and
don't expect a four star hotel every night.
Let your dreaming be your guide.