The seven-member investigative committee, convened by the California-Northern Nevada United Methodist Conference, will determine whether to charge 67 ministers with violating church law for their involvement in the controversial marriage ceremony, held in Sacramento, Calif., in January 1999.
If a church trial determines the ministers are guilty, they could be removed from the clergy.
The two women who were married in the ceremony defended the ministers, saying they deserved praise, not punishment, the Associated Press reported.
"Now we share our church life with the gay community and share our gay life with the church," said Ellie Charlton, who married Jeanne Barnett. "It was very stressful being in two different closets. Now we're not in any closet."
Twenty-five other ministers also participated in the event, but were not named in the formal complaint because they were from churches outside the California-Northern Nevada conference.
The minister who officiated at the wedding, the Rev. Donald Fado, said he believed the ceremony was comparable to an act of civil disobedience. He said he welcomed a church trial as an opportunity to force the church to respond to the needs of its gay members, and described the investigative panel's hearings as enlightening.
"It's like a pastors' school with distinguished scholars," he said. "I've taken notes for future sermons."
The investigative panel, who met in the sanctuary of Community United Methodist Church in Fairfield, Calif., was expected to decide next week whether to bring the charges before a national Methodist conference when it meets in Cleveland in May.
In separate cases in the past, the Methodist church disciplined two ministers for presiding over same-sex marriages and unions.