Thomas Heatherwick was initially shortlisted for the competition, as were Amanda Levete Architects, Caruso St John Architects, Jamie Fobert Architects and Diller Scofidio and Renfro.
These groups are now out of the running following a presentation process held last month.
The competition aims to find designs that will make the ROH’s street-level entrances ‘more open and tantalising’, and make the organisation’s work more visible to the public.
It will also see the Linbury Studio Theatre and the Paul Hamlyn Hall developed, although the ROH’s main auditorium will not be affected.
ROH says it will now work further with the two shortlisted groups before appointing a winner in February 2013.