While the Met was her major home, Chookasian also remained active as a concert performer and sang in opera houses both in the United States and Europe. She quickly became one of the leading contraltos performing on the international stage during the 1960s and 1970s, singing under Georg Solti, Leonard Bernstein, James Levine, Zubin Mehta, Seiji Ozawa, Fritz Reiner, Karl Böhm, Herbert von Karajan, Lorin Maazel, and many other great conductors, with such ensembles as the Philadelphia Orchestra, the Cleveland Orchestra, the London Symphony Orchestra, and the Vienna Philharmonic among others. She was particularly admired worldwide for her performances in Beethoven's Symphony No. 9, Mahler's "Das Lied von der Erde", Schoenberg's "Gurre-Lieder" and above all Verdi's "Requiem". Of the latter work Chookasian stated, "Every note of the Requiem seemed written for my throat". Under Eugene Ormandy she recorded "Das Lied von der Erde" for Columbia Masterworks, and she opened the Saratoga Performing Arts Center in August 1966, again with Ormandy. With Leonard Bernstein, she was one of the many soloists in his recording of Mahler's Symphony No. 8. Among her many other recordings are Beethoven's Symphony No. 9 with the New York Philharmonic under Bernstein, the First Norn in "Götterdämmerung" with the Berlin Philharmonic under Herbert von Karajan, and Verdi's "Requiem" with the Boston Symphony Orchestra under Erich Leinsdorf.