Calvinism a Catholic Invention

First and foremost, Calvinists believe that the Bible itself teaches the doctrines of grace, and of course the Bible predates all the church fathers including Augustine. Also, the Calvinistic doctrine of sola Scriptura states that only the Bible is authoritative in matters of doctrine, and not the fallible writings of even the most esteemed churchmen (a view shared by Arminianism).

The connection between Calvinism and Augustine is that Calvin appealed strongly to Augustine as proof that the doctrines he was teaching were not new, but were in fact taught by a highly regarded church father. This was not because he could not support his arguments from the Bible, but because his Roman Catholic opponents argued that church tradition carried authority, and because they revered Augustine. By appealing to Augustine, Calvin intended to demonstrate that church tradition supported his conclusions. Calvin appealed to Augustine especially with regard to predestination, or as it is frequently known in Calvinistic circles, "unconditional election."

The argument supporting the doctrines of grace as outlined by Calvinism is not one which finds great support or unity in the writings of the early church prior to Augustine, but then again neither does any system of soteriology find great agreement or support in those writings. Prior to Augustine, there was very little written about the doctrines of salvation that did not simply quote or paraphrase the Bible itself. How one interprets these writings depends almost entirely on how one interprets the biblical texts they quote. The early church was generally more concerned with bigger issues, such as: the nature of God (which they finally determined to be Trinitarian); the nature Christ (whom they finally determined to be fully man and fully God); gnosticism; surviving and lapsing under persecution; church government; etc.

In short, no, there is no real "proof" that anyone between the times of the Apostles and the time of Augustine held to a system we would now call Calvinistic. I suspect that even were such "proof" to be found, it would simply be denied or embroiled in controversy just as the biblical texts themselves have been. At the same time, there is also no proof that anyone held to any other well-defined system of salvation. We may guess that such systems did exist, but that they simply did not make it into the preserved writings. I would like to hope that at least one of the systems in place at the time was Calvinistic because I believe that to be the biblical system. However, the church has often fallen into serious and pernicious error, so it would not surprise me if sound theology had been abandoned for many years, just as it was when the entire Christian church supported the Arian heresy that the Son of God was not eternal.