Liturgical practices were not strictly uniform from one community to another, but there was a tendency to view Saint Peter's as the model, and it was at Saint Peter's that some important features of the familiar Roman liturgy took shape. For the eighth-century office celebrated by the monasteries serving Saint Peter's, the evidence is focused largely on the cycles of readings during the night office of Matins. The fourfold liturgical year, centred on Saint Peter's, seems to underlie the arrangement of readings in OR XIV, OR XVI and OR XIVB, representing the period when the great Roman basilicas were staffed by monastic communities, and when Saint Peter's seems to have been something of a model for the other churches of the city. The liturgical leadership seems to have been shifting away from the Vatican basilica, toward the person of the pope himself, whose cathedra or chair was at the Lateran.

The Constantinian peace afforded the opportunity for new spacious church buildings, and a more public celebration of liturgy with more elaborate forms. The Spanish nun Egeria, after a visit to the Holy Land, reveals a well-established liturgical calendar, and describes the various weekday services in the holy city. This chapter traces the growth of liturgy in the ancient churches of Jerusalem, Antioch, East Syria, Egypt, Rome, and the West. At Rome, 15-23 December seems to have been regarded as the end of the agricultural year, perhaps suggesting the theme of the end of history. Christians assembled on the Lord's Day, which seemingly established itself quickly as the weekly worship day. In addition the Didache mentioned fasting on Wednesdays and Fridays. During the fourth century one can see the development of particular feasts and seasons. Egeria mentions Lent, Easter, Pentecost and Epiphany, and indicates that her community in Spain was well aware of these feasts and seasons.