Is it true that no post-apostolic theologians before St. Augustine believed in Eternal Security / Assurance of Salvation? According to Wikipedia in it's entry of 'perseverance of the saints', eternal security has its roots in Church Father St. Augustine of Hippo. Considering that Augustine lived centuries after the Apostolic Age, and the variety of theologians that have predated him (from Origen to Athanasius the Great, Polycarp to Ignatius of Antioch), were the Early Church Fathers really so uniform in thought concerning salvation? 

I find it especially hard to believe because of the fractured and polemical nature of early Christianity, as it was full of controversy and wavering opinions surrounding essential doctrines (ie. Christology).
The answer seems to be NO.  It looks like that a lot of early church fathers taught the doctrine of the Perseverance of the Saints.  Of course they may not call it by that name, or by &quot;Once saved always saved&quot; label (after we translated their writings from Latin / Greek into English), but according to Rev C. Matthew McMahon whose Th.D dissertation is titled Augustine's Calvinism: The Doctrines of Grace in Augustine's Writings, many church fathers taught the doctrine, as shown from a blog article he wrote Did the Early Church Believe the Doctrines of Grace? which contains nicely formatted quotes tagged with the related Calvinist Doctrine.
For example, you can easily see quotes related to the Perseverance of the Saints by doing a web page search for &quot;(Per.)&quot; which yield 15 matches such as:

Clemens Romanus, AD 69: (Per.) “Whereas it is the will of God, that all whom he loves should partake of repentance, and so not perish with the unbelieving and impenitent, he has established it by his almighty will.’ But if any of those whom God wills should partake of the grace of repentance, should afterwards perish, where is his almighty will? And how is this matter settled and established by such a will of his?” (Ep. 1, ad Cor. p. 20).
Irenaeus, AD 180: (Per.) Concerning Christians, “but the Spirit encompasses man within and without, as always abiding, and never leaves him,” (Iren. adv. Haeres. 1. 5, c. 12, p. 450; vide Fragm. Graec. ad Calcem Ireuaei.).
Tertullian, AD 200: (Per.) Tertullian asserts, that the work of God cannot be lost, extinguished, or cease; “for what is of God is not so extinguished, as it is overshadowed; for it may be overshadowed,, because it is not God;. it cannot be extinguished, because it is of God,” (de Anima, c. 4,1, p. 342.).
etc.

The quotes themselves came from Michael Horton's 2011 book Putting Amazing Back Into Grace: Embracing the Heart of the Gospel.