Lieb is leaving his post, which he held for four years, to write a sitcom for Warner Bros. and NBC.
Host Jon Stewart and Rory Albanese remain executive producers, but the Comedy Central show made other changes following Lieb's exit.
Three staffers, Steve Bodow, Jennifer Flanz and Jim Margolis, have been promoted to co-executive producer positions.
Writer Tim Carvell has been elevated to head writer, and line producer Pam DePace will become supervising producer.
In 2009, Lieb released the book, "I Am a Genius of Unspeakable Evil and I Want to Be Your Class President."
The Associated Press contributed to this report.