BRAINTREE -- The Archdiocese of Boston announced the first four pastors assigned by Cardinal Seán P. O'Malley to parish collaboratives March 1.

As part of the phase one implementation of the plan, "Disciples in Mission: A Pastoral Plan for the Archdiocese of Boston," the Office of Pastoral Planning informed the 11 affected parishes at the Masses the weekend of Feb. 23 and 24 after telling parish staffs on the previous Friday.

As the first phase of the plan moves forward, 28 parishes in Belmont, Beverly, Billerica, Brookline, Jamaica Plain, Lakeville, Lynn, Lynnfield, Methuen, Middleboro, Newton, Roxbury, Salem, and Weymouth will link to form 12 collaboratives. Father Soper said all 12 should have pastors assigned by April 7.

"We are now a third of the way through the process of Cardinal Seán assigning pastors for the phase one collaboratives," Father Paul Soper, director of the Office of Pastoral Planning, said.

The assignments gave collaboratives in Beverly, Billerica, Methuen, Roxbury and Jamaica Plain pastors, effective June 4, 2013.

Father Soper said moving slowly and assigning small groups at a time leaves room for careful consideration of each candidate for pastor by the personnel board working on assignments, and the cardinal who ultimately decides every appointment.

"It is far more important to get it right than to get it fast," Father Soper said.

The collaborative in Beverly made up by St. Mary Parish, St. John the Evangelist Parish, and St. Margaret Parish will receive Father Mark A. Mahoney -- who is serving as pastor at St. Rose of Lima Parish in Topsfield since 2007.

Father Shawn W. Allen, pastor at St. Theresa of Lisieux Parish in Billerica since 2011, will lead a collaborative of Billerica parishes made up by St. Mary Parish, St. Andrew Parish, and St. Theresa Parish.

Msgr. William P. Fay, pastor at St. Columbkille Parish in Brighton since 2006, will head to Methuen to lead St. Lucy Parish and St. Monica Parish as a collaborative. Msgr. Fay served as the chairperson for the Pastoral Planning Commision.

Father Carlos F. Flor has led St. Thomas Aquinas Parish and Our Lady of Lourdes Parish in Jamaica Plain, and St. Mary of the Angels Parish in Roxbury since June 2012, and will remain in place there.

Parochial vicars, who assist the pastors in their ministry, have not yet been assigned.

"In general the pastors are part of choosing the parochial vicar for his parish. That has been the case in the past, and that will continue to be the case going forward. We could not assign the parochial vicars before the pastors were in place," Father Soper said.

Pastors previously assigned to the parishes will move on to different assignments after June 4, according to Father Soper. As part of the process, pastors in phase one collaboratives resigned their role as pastors and await reassignment by the archdiocese.

"In order for this to happen a number of pastors had to move on. In fact, at the beginning of the process all 23 pastors submitted to us their letters of resignation. That was an act of extraordinary generosity on their part," Father Soper said.

As part of the plan, Father David Barnes leaves St. Mary and St. Margaret while Msgr. Bill Cuddy leaves St. John the Evangelist in Beverly; Father Jim Kelly leaves St. Andrew's while Father Francis Sullivan leaves St. Mary in Billerica; and Father Patrick Armano leaves St. Monica as Father Rich Burton leaves St. Lucy in Methuen.

In the long term, the plan calls for collaboratives to share not only common pastors, but also pastoral teams, parish staffs, parish finance councils and pastoral councils. The archdiocesan plan organizes its 288 parishes into approximately 135 parish collaboratives.

"I myself had to move out of a beloved parish as a part of this process of pastoral planning. I know it is disruptive in the life of the priest and it certainly is disruptive in the life of the parishes," Father Soper said.

He said that is good, in a sense, because it indicates a healthy bond formed between pastors and the parishes they have lead over the years.

"What we are committed to doing is that as the pastors are chosen, we are going to announce them," Father Soper said.

He said the Office of Pastoral Planning will make announcements public through The Pilot, as assignments continue.

"We know that there are all sorts of things that will make a collaborative work, but the most important decision that we can make about how to accomplish the work is going to be getting the right pastor," Father Soper said.