Overseer was a title used by a number of factions in the Milky Way Galaxy, among them the Androssi of the Alpha Quadrant, as well as the Vaadwaur Supremacy and Confederacy of the Worlds of the First Quadrant of the Delta Quadrant.
An Androssi Overseer often commanded a salvage team, and oversaw all actions carried out. Androssi that had carried out a brave or profitable action in the team were often promoted to Overseer. (SCE eBooks: Cold Fusion, War Stories, Book 1; TNG - A Time to... novel: A Time to Be Born)
In the Confederacy during the 2380s decade, the title of Overseer was sometimes used to refer to the person in charge of a facility, such as the one on the planet Lecahn that produced the Waveforms, but it most commonly refered to members of the Confederate government, approximately equivalent to a minister. In 2381, the Leodt Racha Bralt served as the Confederacy's Overseer of Agriculture. (VOY novels: Protectors, Acts of Contrition, Atonement)