Stair was born in Bethlehem, Pennsylvania. He was ordained as a Methodist minister, but left organized religion, stating "I just call myself a Christian." He moved to the South in the 1950s, saying that God had told him to move there because it would be "the safest place for Christians in the end time."
Stair leads Overcomer Ministry, a conservative Pentecostal Christian organization that runs a widely heard radio-based ministry. Stair purchased a motel in Walterboro, South Carolina in 1978, and encouraged followers to move to the community, sell all their possessions, take a vow of poverty, and donate all that they owned to Overcomer Ministry. The community of about 70 strives for self-sufficiency and simplicity, growing their own food and making their own clothes. Community members live in mobile homes and handmade houses, eating communal meals and gathering for Saturday worship in the Tabernacle. They dress conservatively; women wear long skirts and men wear long pants and shirts with collars. Typically, work is divided along traditional gender lines, with men performing farm/manual labor and women doing domestic chores. Members primarily rely on bicycles for transportation within the community.
Stair broadcasts from a solar-powered radio studio based in the community, often for hours at a time. As of 2014, Stair leases airtime globally on five Free-to-air satellites (Galaxy 19, Hot Bird 8, Optus D2, Thaicom 5, and Eutelsat 25B) and on seven international shortwave radio stations (WHRI, WWRB, WTWW, WWCR, WBCQ, WRMI, and Media Broadcast GmbH) to convey his message to listeners in the United States as well as locations as far-flung as South America, Africa, Australia, New Zealand, Europe, Israel, Russia, India, and Asia. In addition to international satellite and shortwave, Stair also broadcasts worldwide via internet streaming from his ministry's web site and leases time on terrestrial AM and FM radio stations throughout the United States, some of which are large-coverage stations. In the 1990s, Brother Stair was heard on 120 such stations, though by 2007 and continuing through 2014, that total had been reduced to approximately 25. In 2016, however, the broadcast was dramatically increased due to a large contribution which allowed Brother Stair to purchase hundreds of hours per day of broadcasting time to create one of the most extensive shortwave broadcasts in history. Broadcast expenditures of about $1.5 million are funded by donations from listeners. In 1993 and 1994 Stair and his ministry were partners in a failed ship-based radio project due to authorities raiding and confiscating both the ship and its equipment before it could set sail to international waters .
Stair's teachings place a strong emphasis on millennial predictions of world-changing events resulting from divine judgment. In the year 1999, he said that there would be such changes at the dawn of the third millennium. "If the Lord God Almighty does not make a major move before the year 2000," he said, "I'll tell God to go to Hell." Stair also has received publicity over the years for several of his prophecies, including a nuclear confrontation prophesied for 1988, and that Reagan would not complete his term as president. Over the years, Stair has been involved in a number of controversies, including allegations of sexual abuse, of infant deaths, and that his ministry is a cult. Stair objects to medical intervention, and teaches avoidance of doctors. Commune members typically follow Stair's teaching, and in the 1980s and 1990s, local authorities investigated after three infants died during or shortly after birth at the community.
In 2002, Stair, then aged 69, was arrested in Walterboro on two counts of criminal sexual conduct in the second degree. Two women associated with Brother Stair, ages 17 and 20, alleged that he coerced them by "enforcing his religious/personal beliefs" on them. In 2004, Stair pleaded guilty to the charge of assault and battery and was sentenced to time served, a total of 77 days in custody. During his incarceration, recorded programs continued to be broadcast. Stair's conviction caused division in the community. However, about 70 residents remained loyal to him and there are two small branch communities which are part of his ministry.