The Common Onion Orchid has an elongated labellum with crenate edges, whilst the similar Slender Onion Orchid (M. parviflora) has a labellum which is heart-shaped with smooth edges.
Microtis unifolia is listed in the following regions:
Canberra & Southern Tablelands | Southern Highlands | Albury, Wodonga | South Coast | Riverina Murray | New South Wales North Coast | Hume