sentences:  O'Neill made his Metropolitan Opera debut as the Gran Sacerdote in Mozart's "Idomeneo" with James Levine, his Royal Opera House debut as Jenik in Smetana's "The Bartered Bride"  with Sir Charles Mackerras followed by Florestan ("Fidelio") with Antonio Pappano and Salzburg Festival in "Die Zauberflöte" with Riccardo Muti and his Vienna Staatsoper debut as the title role in "Parsifal" with Christian Thielemann.He performed the role of Siegmund in Richard Wagner's "Die Walküre"  at the Royal Opera House, Covent Garden, with Sir Antonio Pappano, Teatro alla Scala and Berlin Staatsoper with Daniel Barenboim, Vienna Staatsoper with Franz Welser-Möst, Bayerische Staatsoper with Kent Nagano, Hamburgische Staatsoper with Simone Young, the Deutsche Oper  and the Metropolitan Opera with Donald Runnicles and in the 2013 Otto Schenk Ring production and in the Robert Lepage production with Fabio Luisi.He made his 2009 debut in the title role of Verdi's "Otello"  with Sir Colin Davis and the London Symphony Orchestra and in 2010 he debuted at the Bayreuth Festival in the title role of "Lohengrin", returning in the title role of "Parsifal" in 2011.