Last week ET's MARK STEINES went exclusively backstage with CHER to talk about her all-new show at The Colosseum at Caesars Palace.

Now, Cher is being joined by none other than TINA TURNER and OPRAH in Las Vegas -- and Mark's got 'em in another ET exclusive!

"This is trouble right here; this is trouble waiting to happen," jokes Oprah.

Lady O and her crew traveled to Sin City for a once in a lifetime opportunity to see these two legendary superstars in action, and now "The Oprah Winfrey Show: Oprah, Cher and Tina in Vegas" is scheduled to premiere this Thursday!

Catch ET tonight for Mark's one-on-three interview with Oprah, Cher and Tina!