Baranski, who plays Leonard's mother Beverly, was last seen on "The Big Bang Theory" in the Season 5 premiere. She currently stars on "The Good Wife" as Diane Lockhart. Her "Big Bang" character will appear via a Skype call.
Baranski has appeared in three other episodes of "The Big Bang Theory" and been nominated for an Emmy for her role twice. So far, other Season 7 guest stars include Regina King.
"The Big Bang Theory" Season 6 premieres Thursday, Sept. 26 at 8 p.m. ET on CBS.