The primary work of nuns, of monastics in general, was the glorification of God, mostly through contemplation and singing the divine office. Singing the hours was a major part of the day. The Rule of St. Benedict, for example, requires that the divine office should be sung seven times a day and once during the night. Everything else fit around that. Over time this work became more and more important and elaborate, especially in wealthier houses. The rise of the Cistercians, however, saw some decrease in the importance of the divine office and a marked increase in the importance of manual labor.
The requirement for manual labor was a more difficult one for nuns to fulfill than it was for monks. Manual labor supplemented and balanced spiritual labor. It also helped communities support themselves. Nuns, however, were generally subject both to stricter rules of enclosure than monks and greater scrutiny in their obedience to said rules, which closed off several avenues of financial support.
Then, of course, there were tasks carried out for the members of the community. The lay sisters of the Gilbertines and other Orders served and saw to the needs of the choir nuns. The kitchen servers, who according to the Rule of Benedict should be ordinary members of the community assigned to the task for a week, the sacristan, the cellarer, and the abbess all had their own work.
All of these were nuns’ work. Contemplation and the singing of the psalms were central, but how that related to other tasks varied widely. Over time, they grew to overshadow nuns’ more earthly tasks, especially in wealthier houses, leading to a division between choir and lay sisters. The 11th and 12th centuries, however, saw some reaction against that. Many, such as the Cistercians and Franciscans, kept the two classes of nuns, but sought more of a balance between spiritual and material work than had previously held.
The Rule of St. Benedict, Chapters 8-20, 31, 35, 48 - Order of St. Benedict
Herlihy, David. Opera Muliebria: Women and Work in Medieval Europe. New York: McGraw Hill, 1990.
Jewell, Helen M. Women in Dark Age and Early Medieval Europe c. 500-1200. New York: Palgrave Macmillan, 2007.
Jewell, Helen M. Women in Late Medieval and Reformation Europe 1200-1550. New York: Palgrave Macmillan, 2007.
Nichols, John A. and Lillian Thomas Shank, eds., Distant Echoes: Medieval Religious Women, Volume One. Kalamazoo, MI: Cistercian Publications, 1984.