Douglass worked on the team that developed the Seventh-day Adventist Bible Commentary, contributing commentaries on five books of the Bible. He was the associate editor of the Review and Herald for seven years. Later he worked at the Pacific Press Publishing Association, first as associate book editor and then as vice-president for editorial development.
Douglass published twenty-four books, mostly commonly on Jesus, Ellen White and perfection in relation to the second coming. His most famous book is arguably Messenger of the Lord: the Prophetic Ministry of Ellen G. White (1988), which was commissioned by the Ellen G. White Estate.
The issue of perfectionism has been an enduring theme within Adventism, and Douglass emphatically supported the impossible possibility of perfection this side of Jesus’ second coming. This strain of perfectionism became known as last generation theology (LGT), which holds that a remnant will be perfect before Jesus’ return. God is waiting for a ripe field to be harvested. That is, when the remnant is ripe or perfect, then Jesus will return to collect his own.
In addition to writing, Douglass also worked as an administrator. He was the president of Atlantic Union College (1967-1970) and Weimar Institute (1985-1992). Douglass also served as the vice-president for philanthropy at Adventist Heritage Ministry and was a consultant for Amazing Facts.