Overseer (or bishop) is one of three New Testament titles for the same office, along with elder and pastor. The word episkopos literally means "one who watches over" — the function of spiritual oversight. In Acts 20, Paul summons the elders of Ephesus (v. 17) and tells them the Holy Spirit has made them overseers (v. 28). They are the same men in the same office; the two words describe different aspects. Elder emphasizes the maturity and authority of the man; overseer emphasizes his function of watching over the flock. In the second and third centuries, the Christian church gradually developed a monarchical episcopate — a single bishop over a city and its multiple congregations — which was a departure from the original New Testament pattern of plural elders in each congregation. Roman Catholic, Eastern Orthodox, and Anglican traditions retain this later hierarchical structure. Presbyterian, congregational, and most Baptist churches preserve the New Testament pattern of plural elders. The qualifications for overseers are identical to those for elders (1 Timothy 3:1-7, Titus 1:5-9). The function is identical: to shepherd, teach, protect, and lead the flock under Christ the Chief Shepherd. The recovery of a biblical understanding of church office means refusing any system that elevates one man above his fellow elders, and equally refusing any system that has no accountability at all.
Acts 20:28 — "Therefore take heed to yourselves and to all the flock, among which the Holy Spirit has made you overseers, to shepherd the church of God which He purchased with His own blood."
1 Timothy 3:1 — "This is a faithful saying: If a man desires the position of a bishop, he desires a good work."
Titus 1:7 — "For a bishop must be blameless, as a steward of God, not self-willed, not quick-tempered, not given to wine, not violent, not greedy for money."
1 Peter 2:25 — "For you were like sheep going astray, but have now returned to the Shepherd and Overseer of your souls."