I've been reading O.C. Edward's magisterial "A History of Preaching", and having arrived at the chapter on the Cappadocians, decided to plunge into the primary sources a bit before continuing on to Chrysostom and Augustine. In my search for good translations of these texts, I came across Faith Gives Fullness to Reasoning , by Frederick W. Norris. This is a great monograph version of Gregory's Five Theological Orations.
Basically, the five theological orations are sermons on theological method that are simultaneously constructive theological proposals regarding the Trinity. In other words, it is the Trinity, Father, Son, and Holy Spirit, who is the source and norm for theological method.
The genius of these orations is this. They reflect on the Trinity. They introduce theological method. They preach. And at the same time, they are fresh and vivid and accessible for even a first time student of theology. If and when I teach a straight up class on theology in the parish, these five orations will be one of the first things we read, of that I am certain.