Patricia Laura Merchant Park last night became the first woman in the Washington area ordained an Episcopal priest with the full blessing of her church.

The two-hour ordination rite, held in the field house of the Episcopal Hich School in Alexandria, was marked by an atmostphere of joy and celebration and was meant to signal the beginning of a new era in the Episcopal Church, which for centuries has restricted its priesthood to males.

Nearly 100 persons - many of them members of Immanuel Church-on-the-Hill where Mrs. Park had served as a deacon for 2 1/2 years - watched the colorful ceremony, conducted by Episcopal Bishop Robert Hall of Virginia.Those present included many who had fought for women priests in the Episcopal church.

After more than a decade of agonizing over the issue, the Episcopal Church at its General Convention last September voted formally to open the previous all-male priesthood to women. The vote, however, was not effective until Jan. 1.

More than two years ago 11 women were ordained in an irregular service in Philadelphia. Mrs. Park who had not completed the requirements for priestly ordination at that time, nontheless had a small part in that service.

The Philadephia ordinations were declared invalid by the Church's House of Bishops, althoug some Bishops disagreed with that decision.

The Philadelphia event served to crystalize feelings on both sides of the issue and led ultimately to two church trials - one in Washington and one in Oberlin, Ohio - of rectors who permitted one or more of the irregularly ordained women to function as priests in their parishes.

Four more women were ordained at similarly irregular rites in Washington 15 months ago.

Although none of the irregularly ordained women has had her priesthood formally recognized by the church, two of them - the Rev. Alison Cheek, and the Rev. Lee McGee - helped distribute Communion during yesterday's service.

Last night, the congregation joyfully shouted the Amens the "Thanks Be to God" and other responses indicted in the ordination ceremony previously reserved for men.They joined prayerfully in the Communion service presided over by the new priest. Afterwards they gathered at the far end of the field house for a stand up pot-luck supper and more rejoicing.

Nearly 100 clergymen and women in ecclesiastical robes - most of them Episcopalian but some from other denominations as well - marched in the processional at the beginning of the service. At Bishop Hall's invitation during the ordination ceremony most of the clergy - including one Roman priest - trooped forward foe the traditional laying on of hands on the head of the new priest. Many added a hug and a kiss as well.

Then, on signal from a meaning beaming Bishop Hall, the entire place erupted into a cacophony of bells of every kind brought by the church members to greet their new priest.

Some opponents of women priests had reportedly sought, unsuccessfully, to secure the use of facilities at Virginia Theological Seminary a few blocks away for protest services. If there were any present last night who opposed women priests, they were not apparent.

Dr. Marian Kelleran, retired Virginia Seminary professor and the first woman to head the world-wide Anglican Consultative Council, took note of the landmark nature of Mrs. Park's ordination in her sermon. She took as her text "fear not," the first two words of the Christmas Angel: "Fear not, I bring you tidings of great joy . . ."

The words "fear not" in the Bible, she noted, "nearly always indicate a new and therefore confusing message" to those being forewarned. By the same token, she went on, the words "fear not" are appropriate words for the church as it is today, and they are appropriate "for the bishop of this diocese" who, she predicted, "would be struggling with calls from irate people who had read about this ordination" this morning.

The words "fear not" are also appropriate "for Pat," who Dr. Kelleran said is "entering an order where there are few other women."

Dr. Kelleran emphasized that the ordination of Mrs. Park will not mark the beginning of "parallel priesthood of men and women in this or any other church . . . there is only one priesthood of the risen Christ."

Mrs. Park was sponsored for ordination by her husband Stephen who is also a priest. The couple together with her other clergy sponsor, The Rev. William Dols, rector of Immanuel, presided over the communion table.