The Jesus Christ Superstar talent search, which began with 3.2 million on July 7, concluded with a consolidated audience of 3.4m between 9pm and 10.30pm.
Ben Forster's triumph attracted an average of 3.17m (14.5%) on ITV1, and 173k (1%) an hour later on ITV1 +1.
The Lloyd Webber format fell below 3m for the majority of its live shows, suggesting that ITV may not commission a similar programme in the future.
From its high last week, 24 Hours in A&E slipped back to 2.3m (10.4%), but added 499k (2.7%) on Channel 4 +1.
Olympics drama Bert and Dickie, starring Doctor Who's Matt Smith, won its 90-minute slot for BBC One with 3.17m (14.8%) from 8.30pm.
Meanwhile, another London 2012-themed broadcast - Britain's Greatest Gold Medallists on ITV1 - bagged 2.26m (11.4%) at 8pm (+1: 169k/1.8%), beating SuperScrimpers's 1.36m (6.9%) for Channel 4 (+1: 225k/1%).
Over on BBC Two, Restoration Home (1.73m/8.8%) and Leaving Amish Paradise (1.46m/6.6%) secured respectable ratings, while NCIS (1.74m/7.9%) and Big Brother (1.14m/6.2%) aired on Channel 5. NCIS added 183k (1%) on timeshift.
Overall, BBC One and ITV1 tied in primetime, both remarkably averaging an 18.2% share, with ITV1 +1 taking 0.9%. Channel 4 claimed third place with 6.5% (+1: 1.1%), ahead of BBC Two's 6.1%, and Channel 5's 5.2% (+1: 0.3%).
BARB ratings data supplied by Attentional