According to Deadline, McDonald has joined the project as a special guest star. O'Hara, Murphy, Michael Cerveris, Debra Monk, Katie Finneran, Celia Keenan-Bolger and John Douglas Thompson have come on board as major recurring guest stars.
A co-production between HBO and Universal Television, "The Gilded Age" is backed by "Downton Abbey" producer Gareth Neame and director Michael Engler. The epic drama follows the millionaire titans of New York City in the 1880s. The lead cast features Christine Baranski, Carrie Coon, Cynthia Nixon, Morgan Spector, Denée Benton, Louisa Jacobson, Taissa Farmiga, Blake Ritson, Simon Jones, Harry Richardson, Thomas Cocquerel and Jack Gilpin.
The nine-part series is created, written and executive produced by Fellowes along with Neame and David Crockett also executive producing. Salli Richardson-Whitfield is also attached as director and executive producer. Sonja Warfield is on board as writer and co-executive producer.