Mark Lamprecht pointed me to this article that denies the claim that premillennialism was the historic faith of the early church. Rather, this article states that they were clearly amillennial. Below is a short excerpt:

By far the early church statement of faith that most vividly presents the early church’s belief in an amillennial, “consummationist” eschatology is The Athanasian Creed. Attributed to Athanasius, the Bishop of Alexandria and the champion of the Council of Nicaea, around 325 A.D., the creed ends with these words: “He shall come again to judge the living and the dead. At whose coming all men shall rise again with their bodies and shall give account for their own works. And they that have done good shall go into life eternal, and they who indeed have done evil into eternal fire. This is the catholic faith, which except a man have believed faithfully and firmly he cannot be in a state of salvation.” Let us analyze these closing verses more carefully to see how they align with the belief system we know today as amillennialism, and how they oppose any belief in an earthly 1000 year reign of Christ.

1. “He shall come again to judge the living and the dead.” This simply means that there will be those who are alive as well as those who are dead when He comes (1 Thess. 4:15). Notice that judgement of the living and the dead occurs at His coming (cf. Matt. 25:31-46), not a thousand years after His coming.
2. “At whose coming all men shall rise again with their bodies ….” Thus, at Christ’s coming all rise, the good and the evil alike (cf. John 5:28,29, Matt. 12:41,42). Not just the good, and then a thousand years later the wicked.
3. “… and shall give account for their own works. And they that have done good shall go into life eternal, and they who indeed have done evil into eternal fire.” This is a clear reference to Matt. 25:31-46. Athanasius views this as taking place after the resurrection (or translation), making it a post-resurrection judgement. This is in sharp contrast to the dispensational view that Matthew 25:31-46 is only a judgement of “living, mortal Gentiles” who survived the tribulation. Note again that it (i.e. Matt. 25:31-46) is viewed as a judgement of all men, the Jew and the Gentile, the wicked as well as the good.

You can read the full article here.