The BBC's Any Dream Will Do beat ITV's Grease Is The Word in the battle of the musical talent hunts.
Any Dream Will Do is hosted by Graham Norton
Six million people tuned in to see the 12 finalists who will compete for the lead in a West End production of Joseph And The Amazing Technicolor Dreamcoat.
They will compete for public votes in a live weekly show on BBC One.
ITV's Grease Is The Word - whose judges include 1980s star Sinitta and David Gest - made its debut on Saturday, attracting an average audience of 4m.
The ITV1 reality show will aim to fill the parts of Danny and Sandy in a new West End stage production of Grease opening next summer.
It will follow wannabe stars from the first auditions to the live finals, where eight couples will compete for the star roles.
The 12 Josephs, selected by Andrew Lloyd Webber and his panel of musical theatre experts, follows on from last year's How Do You Solve A Problem Like Maria...? which was won by Connie Fisher.
The Joseph finalists, handpicked from thousands of hopefuls, were revealed to the public on Saturday night's show.
Sinitta and David Gest are among the judges on Grease Is The Word
They include Antony Hansen, 17, from Abington, near Oxford; Ben Ellis, 18, originally from Scarborough; Chris Barton, 19, from Ormskirk, Lancashire; and Keith Jack, 19, from Dalkeith, Midlothian. All are currently studying performing arts or musical theatre.
They are joined by clothes shop assistant Chris Crosby, 18; Johndeep More, 23, an office administrator from Birmingham; and Robert McVeigh, 23, a builder from Rotherham.
Craig Chalmers, 25, is an entertainer from Edinburgh; 27-year-old actor Daniel Boys was Adam Rickett's understudy in Rent; and Lee Mead, 25, has been a professional singer and actor for five years.
Other contestants include Seamus Cullen, 35, a sales and marketing worker from north London; and Lewis Bradley, 17, from Middlesbrough, who got down to the final 15 for the film version of Billy Elliot.
Over the next eight weeks, they will perform for Lord Lloyd Webber and his panel - Denise Van Outen, theatre producer Bill Kenwright, Torchwood star John Barrowman and vocal coach Zoe Tyler - to prove they have the ability to make it onto the stage.