Dr. Mc Steamy, Eric Dane, wifey and alleged madam in 3-way-sex tape shocker.

Dane and his wife Rebecca Gayheart "star" in a naughty video streamed on Gawker.com.

The Tinsel Towners appear completely nude and out-of- it in a 12 minute vid shot in former starlet Kari Ann Peniche's pad as they discuss what porn names to use.

Gayheart at one point says she needs to lie down because she feeling "very high".

They then discuss erasing the tape  -- but it never was.

It was seized as evidence by LAPD when they were searching for Peniche's client list of "johns", according to Gawker.

Peniche, 25, was crowned Miss USA 2002 but lost her crown for posing for Playboy and most recently was being treated for sex addiction on Celebrity Rehab.

Peniche claims the tape had been stored on her hard drive and then stolen by Rehab roomie troubled country star Mindy McCready.

How it made it online is as yet unknown.