Heineken Cup holders Leicester Tigers and Munster are both there for a third time and Llanelli are through to the semi-finals for the second time, four nations retaining an active interest in the showpiece matches to be played on April 27/28.
The open draw means that the first and third teams drawn at random will have "home" advantage in the semi-finals, in that the matches will be played in that team's country and at a stadium capable of accommodating a crowd in excess of 20,000.
The draw, to be televised live by BBC Wales, will be conducted by Jean-Pierre Lux, Chairman of ERC, and Lions and Wales scrum half legend Gareth Edwards - recently voted the world's greatest player.
In addition, leading players and officials from all four teams will be in attendance and available for interview / picture opportunities following the draw.
"This is only the second time in the history of the tournament that we have teams from four different nations represented in the semi-finals," said Derek McGrath, ERC Chief Executive. "This is a great opportunity for fans in those countries to get behind their teams and support them in their quest to reach the Heineken Cup final at the Millennium Stadium, Cardiff, on 25 May."
Around 46,000 went through the turnstiles - a full house of 16,249 at Welford Road to watch Leicester Tigers beat Leinster 29-18 the top attendance - with a bumper armchair audience of well over 7m tuning into BBC, FR2, RTE and ITV Sport.
BBC Grandstand had to juggle their schedule when the Bath Rugby v Llanelli match was postponed for 24 hours due to a water-logged pitch. But they still attracted an audience of 2.9m for Munster's 16-14 victory over Stade Francais in Paris and then 2m for Sunday Grandstand audience when Llanelli beat Bath 27-10.
FR2 viewers had a bumper marathon Saturday, 2m first watching Castres Olympique pip Montferrand 22-21 and then Munster's away triumph.