These days it varies house to house. Most in the U.S. pray in English, using a wide range of musical styles.
There *was *formerly a standard Cistercian office, which was essentially that of the Rule of St Benedict, published jointly by the Strict Observance (Trappist) and Common Observance Cistercians. It was in both Breviary (text only) and Antiphonale (with chant notation) forms; those books are pretty hard to come by. Cistercian chant is somewhat simpler than conventional Gregorian chant, but recognizably of the same musical idiom.
As in many monastic houses, some Cistercian communities have pretty much assembled their own office books; some use something similar to the Liturgy of the Hours. The traditional Cistercian office differs from the traditional Benedictine office primarily in the hymns. The very earliest Cistercians wanted to abide by the literal text of the Rule, so where the Rule specifies an “Ambrosian” hymn, the Cistercians wanted to use only hymns that they understood to be clearly written by St Ambrose. Therefore, the Cistercian office has fewer hymns but uses some of them with much greater frequency than the Benedictine office.
In recent editions before the Second Vatican Council, the Cistercian office concluded with a commemoration of Mary: The “Sub tuum praesidium” every day at Lauds (except on Marian feast days); Salve Regina after Compline every day throughout the year; the conventional seasonal Marian antiphons at Vespers (Alma Redemptoris Mater, Ave Regina Caelorum, and Regina caeli); and “O holy Mary, help thou the suffering…” at Vespers during the rest of the year.
This question is close to my heart, as I have been an “office addict” for more than 30 years, and I spent eight months as a postulant in a Cistercian abbey!