I believe some of the Church Fathers hold to some form of Consubstantion. I'll see if I can find some sources for you.
Protestants like to quote this passage from pope Gelasius I's Tractatus de duabus naturis Adversus Eutychen et Nestorium
« Surely the sacrament we take of the Lord´s body and blood is a divine thing, on account of which, and by the same we are made partakers of the divine nature; and yet the substance of the bread and wine does not cease to be. And certainly the image and similitude of Christ´s body and blood are celebrated in the action of the mysteries.
Certe sacramenta, quæ sumimus, corporis et sanguinis Christi divina res est, propter quod et per eadem divinæ efficimur consortes naturæ; et tamen esse non desinit substantia vel natura panis et vini. Et certe imago et similitudo corporis et sanguinis Christi in actione mysteriorum celebrantur. »
I would like to have the entire text, but I do not know where to find it. It is said to be in the supplements of the Migne edition, but the library where I can find the Migne volumes do not have the supplements. The reference is: Jacques Paul Migne, Patrologia Latina, Tractatus de duabus naturis Adversus Eutychen et Nestorium
14, PL Supplementum III, Part 2:733 (Paris: éditions Garnier Frères, 1964).
The debate is heated between Roman Catholics and Protestants because the text, being a tractatus
, looks like an ex cathedra