An extraordinary month of warm, sunny weather has raised interest in the family-friendly summer encounter which is to be played on a day of celebration for 130 years of Welsh Rugby ahead of Wales' Rugby World Cup campaign in New Zealand.
Over 60,000 fans headed to the Millennium Stadium for Wales' sizzling June fixture against World Champions South Africa last season and the WRU is expecting another bumper crowd when Warren Gatland's Wales face the Baa Baas.
Millennium Stadium General Manager Gerry Toms said: "Wales versus the Baa Baas in Cardiff on Saturday 4th June promises to be the very best day out this summer for families.
"As well as the world-class rugby action, there's so much on offer for families and I'm delighted that, as parents across Wales plan for upcoming holidays, they are snapping up tickets to enjoy another exciting day out at the Millennium Stadium.
"The special ticket prices set for Wales versus the Barbarians and the Saturday afternoon kick off time will encourage families and groups to head for Cardiff early.
"Fans can enjoy the capital city before heading to the Stadium for a very special rugby occasion which will offer a full-programme of entertainment, including a choir of up to 1,000 voices singing before and during the game."
Rugby fans can still get tickets for the summer RWC warm-up game against the Barbarians priced at £40 and £30 for adults and £100 for a family ticket (2 adults 2 children)
For the Baa Baas game there has also been a new pricing category introduced this season which offers £15 tickets for the under 18s enclosure.
Tickets can be purchased online at www.wru.co.uk/tickets or by calling the ticket hotline 08442 777 888 or Ticketline on 02920 230130.