Koscheck first broke the news of his participation on UFC 106 late Tuesday night on his Twitter account.
"I got some big fight news for me. I am fighting nov 21 in Vegas. Co main event!!! Haha it's on baby!!!!" said Koscheck in the post.
Koscheck vs. Johnson will likely serve as the co-main event of UFC 106, with the promotion needing to fill that void. The original UFC 106 co-main event of Tito Ortiz vs. Forrest Griffin is now the event's main event after original UFC 106 headliner Brock Lesnar vs. Shane Carwin was cancelled due to Lesnar being stricken with a serious case of the flu.
Koscheck is also slated to face Mike Pierce at UFC Fight Night 20 in January, however, it is not yet known if he will sitll take that bout or not.
Koscheck (13-4) has been back and forth as of late, going 2-2 in his last four bouts. He rebounded from a shocking upset loss against Paulo Thiago in February, to most recently defeat 12-year veteran Frank Trigg at UFC 103 in September.
Johnson (8-2) has won his last three bouts inside the Octagon, with all of his wins being by stoppage. He most recently defeated Yoshiyuki Yoshida via first-round TKO at UFC 104 on Oct. 24. Johnson has put together a 5-2 UFC record, with other notable Octagon wins coming over Luigi Fioravanti and Kevin Burns. He possess powerful and explosive striking skills, having finished six of his eight career wins by TKO or KO.