In Ancient Christian Worship: Early Church Practices in Social, Historical, and Theological Perspective, Andrew B. McGowan describes the early church’s Eucharist as a Greco-Roman banquet.
A deipnon (or in Latin, a cena or convivium) was an evening meal with certain expected formalities and a tradition of proper conduct; as an institution, the ancient Greco-Roman banquet includes and defies modern categories of secular and sacred, familial and public, celebratory and solemn. Ancient banquets were relatively formal and purposeful events, held often but nonetheless distinguished from merely incidental eating. They could be large or small, ostentatious or austere, civic or familial. They were also an integral part of Greco-Roman (including Jewish) sacrifices, since the flesh of animal victims was often consumed straight after ritual slaughter in a festive atmosphere. Groups bound by kinship and by professional, social, religious, or ethnic ties celebrated such meals together to create and express their identity and their beliefs when need or opportunity for celebration arose. . . .
There were expected features of ancient formal dining, although much variety in detail. We hear of participants gathering in a dining room, or triclinium, often reclining on couches arranged around the room as three sides of a rectangle like an angular U. In some places, and especially in later antiquity, diners might form their party around a C- or crescent-shaped table, or stibadium; the earliest surviving depictions of Christian meal scenes, such as those in the Roman catacombs, present such curved assemblies, as do the oldest images depicting Jesus’ Last Supper. . . .
Preliminaries for the banquet could include washing of hands, offering of an opening prayer or hymn, and libations. The meal proper followed, with the variety and quality of foods depending on the means of the host or group and on the nature of the occasion. After eating, tables were removed and wine was brought and mixed with water, typically in a large bowl, or kratēr, and then shared by the diners in individual cups after further prayers or libations to the relevant deity. A number of such large bowls of mixed wine might be prepared over the evening—three was regarded as ideal. Entertainment and/or conversation was expected during this time, its form depending on the group. Such diversions ranged from the subdued conversations of philosophers to more raucous events involving flute girls and courtesans. . . .
McGowan envisions early Christian assemblies as taking the form of an evening banquet held in the homes of wealthy patrons or in other facilities suitable for such an occasion. Participants reclined at the table. After the introductory rites and blessings, a simple but filling meal of bread and wine (mixed with water) – and perhaps some vegetable side dishes – would follow. McGowan believes that both the bread and the wine would have helped supply the caloric requirements of the poorest among the assembly. Meat was probably not commonly served for two reasons. First, meat was expensive; only the wealthy members of the assembly could afford it. Serving meat would have been socially divisive. Second, most of the meat in the market came from animals slaughtered in pagan temples. Meat was too closely associated with idol worship to be welcome in a Christian assembly.
Most of what modern people associate with worship would take place after the meal, during the “entertainment” portion of the banquet commonly called the symposium. After the meal, scriptures would be read, exhortations delivered, prophecies proclaimed, prayers prayed and songs sung.
The banquet form of the Christian Eucharist endured into the third century. As the church grew in size, however, it became increasingly difficult to replicate this intimate experience on a large scale. When the principle assembly moved from an evening meal to a Sunday morning gathering, a leisurely banquet was out of the question for those who had to go to work. Moreover, Christians increasingly saw the meal in sacrificial and cultic terms (a process that deserves its own discussion). Eventually, then, the banquet evolved into the token of bread and wine that we know today.