Karen Walker will be performing on the Vineyard this summer. Well . . . sort of. Emmy Award-winning actress Megan Mullally (inset), best known as the boozing, boisterous socialite from “Will & Grace,’’ will take the stage but in a completely different role alongside her hubby, “Parks and Recreation’’ star Nick Offerman, when they present their comedy-variety show “Summer of 69: No Apostrophe.’’ The power couple’s Aug. 29 appearance is part of Mark Cortale’s Broadway concert series at the Martha’s Vineyard Performing Arts Center this summer. It features an impressive lineup of award-winning stars from the stage and screen, starting with Vanessa Williams on July 9 and Megan Hilty on July 16. SiriusXM Radio host Seth Rudetsky will serve as the host-pianist for these first two concerts. On Aug. 14, Kristin Chen­-oweth will appear with Mary-Mitchell Campbell on piano, and on Sept. 2 Patti LuPone will present her show “Coulda, Woulda, Shoulda’’ with music director Joseph Thalken tickling the ivories. To purchase tickets, visit www.vineyardbroadway.com.