Is “Once Saved, Always Saved” the full biblical doctrine of eternal security or only a diluted version of it? This article argues that OSAS affirms an important truth but often leaves out the equally biblical doctrine of perseverance. Readers will see how Scripture presents salvation as both God’s preservation of his people and their continuing faith in Christ to the end. The article examines key passages in the Scriptures. It also explains how biblical warnings against apostasy function as means God uses to preserve believers rather than as denials of eternal security. Historically, the discussion traces the doctrine from Augustine through the Reformed confessions and shows why OSAS is better understood as a later, thinner abbreviation of the fuller doctrine of the Preservation and Perseverance of the Saints. Readers will discover why true assurance rests not merely in a past profession of faith, but in God’s continuing grace that sustains faith, repentance, holiness, and endurance. The article ultimately argues that those whom God truly saves, he preserves, and those whom he preserves persevere until final glorification. A companion podcast episode is also available there for those who prefer listening over reading.