LINTHICUM HEIGHTS, Md. — Cal Oren was threading his way through the Santa Cruz Mountains of California early one evening in 1993, driving his wife, brother and three tired children back from a day of hiking amid the redwoods. As their car neared the town of Ben Lomond, Mr. Oren said, his brother pointed to a church on the roadside and said: “I’ve been inside this. It’s really neat.”

So Mr. Oren pulled to a stop, and as the children stayed in the car, the grown-ups gingerly padded into the sanctuary of Saints Peter and Paul Antiochian Orthodox Church. A lifelong Presbyterian, Mr. Oren knew virtually nothing about the Antiochians or, for that matter, Orthodox Christianity in general. He had always associated Ben Lomond with hippies, geodesic domes and marijuana fields.

As he entered, a vespers service was under way. Maybe two dozen worshippers stood, chanting psalms and hymns. Incense filled the dark air. Icons of apostles and saints hung on the walls. The ancientness and austerity stood at a time-warp remove from the evangelical circles in which Mr. Oren travelled, so modern, extroverted and assertively relevant.

“This was a Christianity I had never encountered before,” said Mr. Oren, 55, a marketing consultant in commercial construction. “I was frozen in my tracks. I felt like I was in the actual presence of God, almost as if I was in heaven. And I’m not the kind of person who gets all woo-hoo.”

The ineffable disclosure of that evening, a 15-minute glimpse into Byzantium, rattled everything certain in Mr. Oren’s spiritual life. Even as he and his family kept attending a Presbyterian church near their home in suburban Baltimore, he stepped down as a ruling elder and Bible-study instructor. In 1995, he attended his first service at Holy Cross, an Antiochian church here, about 10 miles south of Baltimore. By late 1996, he was a regular, and in May 1997, he and his family converted and joined.

Any person’s conversion is by nature an individual and idiosyncratic journey, and Mr. Oren’s reflected not only his visceral sense that Orthodoxy had a “core of holy tradition” but also his intense concern over theological concepts like giving the Eucharist to baptized infants, which may not animate other believers quite the same way.

Yet in its broader outlines, his movement from the Protestant realm into the Orthodox one, specifically into the Antiochian branch, attests to a significant and fascinating example of denominational migration. Over the last 20 years, the Antiochian Orthodox Church — with its roots in Syria and Lebanon and its longtime membership in the United States made up almost entirely of Middle Eastern immigrants and their descendants — has become the destination of choice for thousands of Protestants of Northern European ancestry.

The visible shift began in 1987 with the conversion of nearly 2,000 evangelical Christians, led by Peter E. Gillquist and other alumni of the Dallas Theological Seminary and the Campus Crusade for Christ. More recently, a wave of converts has arrived from such mainline Protestant denominations as the Episcopalian and Lutheran.

Some 70 percent of Antiochian Orthodox priests in the United States are converts, according to Bradley Nassif, who, as a theology professor at North Park University in Chicago, is a leading scholar of the religion. A generation or two ago, Professor Nassif said, converts made up barely 10 percent of Antiochian clergy.

Professor Nassif went so far, in a 2007 article in Christianity Today magazine, as to suggest that the 21st century might become the “Orthodox century” as disenchanted Protestants grew attracted to the historical roots, theological rigor and social conservatism of the Eastern Christian denominations.

Whether or not the prediction pans out, it is certainly true that no American convert comes to the Antiochian church by convenience or ease. The denomination has only about 250,000 members in 250 congregations in the country, Professor Nassif estimated. Worshippers stand during most of the two-hour Divine Liturgy each Sunday. Nearly half the days in the year require fasting from meat, dairy, eggs and most fish.

Yet when Mr. Oren and his family joined Holy Cross, they found kindred spirits in more ways than one. The church’s pastor, Father Gregory Mathewes-Green, had left the Episcopal ministry to convert. His wife, Frederica Mathewes-Green, had written perhaps the definitive book on the subject, “Facing East: A Pilgrim’s Journey Into the Mysteries of Orthodoxy” (HarperOne, 2006).

Alienated by what he called “spiritual and theological chaos and moral confusion” in the Episcopal Church, Father Mathewes-Green, 62, started Holy Cross in early 1993 with 19 members, five of them from his own family. When he formally renounced his Episcopal vows, he lost not only his annual salary but also the rectory that was his home.

“There were many times,” he recalled in a recent interview, “when I thought, ‘Today is the day I have to look through the Help Wanted ads.’ ”

In the years since, though, Holy Cross has grown to 120 members, nearly two-thirds of them converts, and has bought and paid off a $265,000 building. Fittingly for a congregation of spiritual seekers, Holy Cross occupies a stone structure built by Methodists and most recently occupied by the Pentecostals of the Korean Full Gospel New Generation Church.

While the sun streams through a stained-glass window of Jesus that was installed by the original congregation, most of the icons were painted within the last dozen years by an Orthodox convert, Carolyn Shuey. The other day, Father Mathewes-Green was tutoring the latest prospective convert, a Roman Catholic immigrant from Congo.

The unexpected evolution of the Antiochian Church has had only one drawback, at least at Holy Cross. When Father Mathewes-Green was persuaded several years ago to raise money with a church supper, people flocked to Holy Cross, expecting the savory specialties of the Levant. What they got was the culinary outcome of the priest’s former life as an Episcopalian from South Carolina: hot dogs and brownies.

The fund-raiser, all prayers and chants to the contrary, was a loser.