This priest of almost 30 years is about to become a bishop, to vacate the small parish office where he's spent so much of the last decade. He sits there now, in the cool stillness of late afternoon, reflecting on what those years have taught him.

"I was caught to a degree in what went on in the '60s," the Rev. A. Theodore Eastman is saying, "when people felt that the real action was somewhere out there in the world, marching in Selma and demonstrating in front of City Hall . . . . "

The goals were worthy, but "in some ways clergy were mistaken in those years," he says, counting himself among the mistaken, among those who "would jump out ahead and do it" when the people were not interested or seemed to be moving too slow.

He has learned not to do it for people, says Eastman, now 53. "I think the harder task was to move the congregation along so that the people would do those things, and I guess that's where I think we are called to work . . . . We're enablers."

Enablers. The idea has been at the heart of Eastman's low-key style and his mission as rector of St. Alban's Church in Northwest Washington for the past 8 1/2 years.

And it marks his approach to his new duties as bishop coadjutor of the Episcopal Diocese of Maryland, a post he will assume in ceremonies next Saturday at Washington Cathedral amid pageantry refined by the centuries--trumpets and trombones sounding Frescobaldi's "Canzona" to introduce the bishop-elect, a procession of a dozen bishops, a 250-voice choir intoning ancient hymns, plus organ and tympani.

At the center of all that splendor, before an audience expected to exceed 3,000, will be Eastman--a man who sees himself as "no more important than anybody else" in his "friendly local neighborhood parish," who talks more proudly of the accomplishments of his wife and three children than he does of his own, who sees himself as going to Maryland to be a "member of the team."

He leaves a 1,300-strong congregation that made major adjustments during his tenure, a period marked by significant changes within the Episcopal Church--among them ordination of women and modernization of the liturgy.

Eastman supported the movement to allow women "full rights and privileges of office at every level in the church" and brought in a woman seminarian to do field work at the parish just before the canon permitting women's ordination was passed in 1976. The seminarian, the Rev. Vienna Anderson, is now one of the associate rectors at St. Alban's.

Some left the church "but not a significant number," Eastman says. "There are some people in the congregation who are still uncomfortable with women clergy but they're hanging in there." There are also people "who would go to Vienna for counseling who would not come to me," he adds.

Eastman also helped lead the way in preparing his congregation for the updated prayer book he knew was due. That too came in 1976. "Some people have been put off by that," he says, but most are starting to appreciate the new text.

But perhaps his greatest satisfaction, he says, has been the recognition by many parishioners that ministry is not limited to clergy: "We've got a lot of people in the Congress . . . in this congregation, and those people have tremendous power and tremendous ability to do something for society." His role, he says, has been to help church members "think theologically about what they do."

Eastman will turn to some new tasks in the days ahead, as he and the present bishop of Maryland, the Rt. Rev. David K. Leighton Sr., administer the diocese, which encompasses Western Maryland, Baltimore and surrounding counties. (The Washington diocese covers four counties in this area, and there is also an Eastern Shore diocese.)

Unlike suffragan and assistant bishops, who do not automatically succeed the bishop when he retires or dies, a bishop coadjutor is elected precisely for that purpose, and must be voted for by two separate bodies of clergy and laity and approved by a majority of the church's diocesan standing committees and 246 bishops. Leighton plans to retire in five years.

Until then, Leighton is in charge, but he must give the coadjutor specific areas of responsiblity for which the latter wields full authority.

"I've teased Bishop Leighton about this because I think I've got all the good stuff," says Eastman. Among his duties will be missionary development, urban work, advocacy programs, social services, and visitations to half the diocese's parishes, schools and nursing homes.

Eastman is no stranger to missionary work, having helped found the Overseas Mission Society, a voluntary organization. During his 12 years with OMS until it folded in 1968, he spent six months in Tokyo, a summer in Cuba just before Castro took over, and 10 months in Eastern Europe studying the status of churches there. There were also travels to Africa and Latin America.

He worked to spread the missionaries' messsage back home: "If Christianity is going to speak to a culture then it has to come out of the culture and not be imposed by people with a different set of values or different visions or different cultural heritage."

His embrace of that view began with a summer trip to Mexico in 1952, midway through his three years at Virginia Theological Seminary, and solidified during his first appointment in Gonzalez, a tiny town of mostly Mexican field workers in the Salinas Valley of his native California. He spent 3 1/2 years there building a church "from scratch--there was no Episcopal church, just a handful of people that wanted one." After the church was established, he left, headed for OMS.

When OMS ended because of dwindling church interest in missionary work outside the country, Eastman did ecumenical work for the national church leadership for a year, then took on a pastorate in Allentown, Pa., where he stayed for 4 1/2 years before coming to St. Alban's.

That diversity of service helped make Eastman well known within the church. Before his election in March for the Maryland office, he was nominated four other times, twice as suffragan bishop for Virginia, once as bishop coadjutor for North Carolina, and once for bishop of Hawaii, a nomination he turned down because he had just moved to Allentown. He was also under consideration for a coadjutor post in California.

With his election in Maryland, he will now move with his family to Baltimore, the diocesan headquarters.

"Being a parish minister is probably good training for going into this other vocation," he says. "You have to be a lot of different things to a lot of different people." The ability to look after the clergy is important, but so are encounters with the wider community. That means being "willing to be a prophet sometimes," acting on convictions while staying in tune with the people.

At the top of the agenda is nuclear disarmament, which Eastman sees as a major concern.

Poverty is another problem to be tackled early, especially in light of gaps he sees in the Reagan administration's safety net. He says poverty reflects "huge, huge issues" that are beyond the resources of the private sector alone.

"People are not always altruistic," he points out, "and sometimes they have to be shoved and pushed and coerced a little to do what's right. . . The voluntary sector has no coercive powers. The government does."

While acknowledging that the administration "may have helped us to see . . . that maybe we've relied too much on the government and we need to look at some other ways of solving some issues," he emphasizes that the solutions must be reached "in partnership."

Eastman believes churches can capture the imagination of those hungering for faith by showing willingness to help the poor:

"If we can show that we're serious about that and can translate some of the splendor that will be evident in the service on the 26th of June into the social action of people, then that will be a powerful message."