Q: What is the history of the Easter Vigil being the moment for the elect celebrating initiation?
A. This is a great question! I wish there were an equally great answer. The truth is, it’s complicated.
There are really two questions here. When did the church start celebrating the Easter Vigil, and when did the Easter Vigil become the premier moment for celebrating initiation?
The New Testament doesn’t talk about an Easter Vigil, much less baptisms at the Vigil. What is clear in the New Testament is that the first disciples celebrated the Lord’s Day. And they baptized. But not always at the same time.
We don’t hear about an annual celebration of Easter until the second century. However, scholars conclude from these early writings that an annual Easter feast probably started in the first century.
But when that annual feast was celebrated differed. In the churches of Asia Minor and Syria, Easter was celebrated on the day of the first full moon of spring, no matter what day of the week that fell upon. In the churches of West, including Rome, Easter was celebrated on the Sunday after the first full moon of spring. These two different practices continued until the Council of Nicaea (325) standardized the western model that we still have today.

When did baptisms start happening on the Easter Vigil?

However, it is not clear that initiation was necessarily celebrated on Easter in those earliest days. We don’t get a clear indication of that until a third century letter written by Tertullian, a Christian author in Africa. Tertullian said that Easter is the day that has the “most solemnity” for celebrating initiation and that Pentecost would be the next-best day. But then he goes on to say that any day, really, is a good day to baptize because all days were created by the Lord.
So for any time before the fourth century, the most we can say is that there was a preference for celebrating initiation at the Easter Vigil, but there was no standard practice. And that preference was probably limited to Rome and North Africa.

Then, in the fourth century, the church began a historicization of the liturgical year. There was an attempt to make Jesus’s life and ministry fit into a story that could be told in an annual calendar cycle. For the first three centuries of church history, the only “feast days” were the weekly Lord’s Day and the annual memorial of Easter. In the fourth century, the full structure of the Triduum evolved as well as the liturgical celebrations of Lent and the fifty days of the Easter season, including the feast of the Ascension. The Advent-Christmas cycle also developed at this time.
And while there were always exceptions, in the fourth century the celebration of initiation at the Easter Vigil became the norm.
This did not last long, however. Toward the end of the fifth century, the adult catechumenate began to die out as the church shifted to an emphasis on infant baptisms. Once the catechumenate died out, the Easter Vigil became less and less important in the church calendar. It was not until the Holy Week reforms in the 1950s under Pope Pius XII that the Easter Vigil was restored to its central importance in the church calendar. However, we still did not have adult baptisms at the Vigil. That would not happen until the reforms of the Second Vatican Council.

What changed for the Easter Vigil at the Second Vatican Council?

In the Constitution on the Sacred Liturgy in 1963, the bishops called for a restoration of the catechumenate. That restoration was accomplished with the promulgation of the Rite of Christian Initiation of Adults in 1972. That document also restored the norm of the fourth century church:

The usual time for the celebration of the sacraments of initiation is the Easter Vigil. (RCIA 207)

However, as has always been the case, for unusual circumstances or pastoral need initiation may be celebrated on other days. However, the rite of election and all the rites usually celebrated during Lent must also be celebrated with a similar spacing of intervals between the rites that we usually have (see RCIA 26).
If you want to read even more about the history of the liturgical year and the rites of initiation, see these two books:
The Liturgical Year: Its History & Meaning after the Reform of the Liturgy by Adolf Adam
The Rites of Christian Initiation: Their Evolution and Interpretation by Maxwell E. Johnson

Your turn

What questions have your seekers and catechumens asked about when their baptism will happen? What are some of your clearest memories of baptisms at the Easter Vigil? Share your thoughts in the comments below.