He will report to Nils Larsen, a private-equity executive who has also been CEO of the Tribune Broadcasting since May. Among Cook's roles will be assisting with sales operations and guiding the stations in developing original programming.
Cook, who formed MBN Inc. after a decade leading Twentieth, "brings a fresh perspective and a variety of new and interesting ideas about where the industry is heading and how we should position our broadcast operations," Larsen stated.
During his tenure at Twentieth, the company distributed shows such as "Family Guy."
Tribune runs 23 stations, including the CW affiliates in the country's three-largest markets and Fox stations in San Diego and Indianapolis.
At Twentieth, one of Cook's misfires was attempting to use English-language telenovelas -- the serial dramas that run nightly and are popular on Spanish-language television -- as the anchor for MyNetworkTV.
Cook oversaw much of the network's launch. Since its 2006 debut, it has gone through several iterations before settling on off-net dramas as the anchor.