O'Hara returned to Lincoln Center Theatre to star as Anna Leonowens in the Broadway revival of "The King and I" opposite Ken Watanabe as The King. The production began previews at the Vivian Beaumont Theatre in March 2015 and opened in April 2015. This role won O'Hara her first Tony Award. O'Hara's final performance as Anna was in April 2016. She gave her debut solo concert at Carnegie Hall in October 2016 and guest-starred as the recurring character Dody on the fourth season of "Masters of Sex". She played Fiona in the "Encores!" production of "Brigadoon" at New York City Center in November 2017. Jeremy Gerard of "Deadline Hollywood" called O'Hara's performance "luminous", writing: "O’Hara is impossibly beautiful, vocally and in conveying Fiona’s romantic determination and heartbreak." Also in 2017, she starred as Kate Bonner in Season 1 of the web drama series "The Accidental Wolf", receiving a 2018 Primetime Emmy Award nomination.