In her previous role, McGrath was responsible for MTV, MTV2, VH1, CMT, Comedy Central and the recently announced gay network Logo.
In her new role, which starts immediately, she will oversee her previous remit plus Nickelodeon, Nick at Nite, Spike TV, TV Land, Noggin, The N, MTV Networks digital suite, MTV Networks International and all of the company's related consumer products and digital businesses.
She will report directly to Feston, who has assumed the role of co-president and co-chief operating officer at Viacom. Mark Rosenthal, president and chief operating office of MTV Neworks, is leaving the company.
Freston said: "Judy is the perfect fit for this job. Ours is a business of creative vision, smart brand building, unrelenting consumer focus and good execution. We are riding at an all-time high now, clearly the industry leader, and I feel very proud and fortunate to be able to turn this job over to Judy and very much look forward to seeing her influence on the company grow and grow."
If you have an opinion on this or any other issue raised on Brand Republic, join the debate in the .