A group of Baptists started meeting in Largo from around 1778 but it was not until 1790 that Dr Goodsir, along with Thomas Paterson became joint pastors of a more formalised church. Both men were already lay preachers. Goodsir had been part of various churches in his earlier life but in 1789 he became a Baptist. It would appear that he gave his services free and largely unassisted for around 25 years until his death in 1816.