Okay, been doing research on what exactly to Orthodox believe on the matter, and I came across some Orthodox Catechisms that talk about the subject:
From the Catechism of St. Philaret (Drozdov) of Moscow
338. What is the most essential act in this part of the Liturgy?
The utterance of the words which Jesus Christ spake in instituting the Sacrament: Take, eat; this is my body. Drink ye all of it; for this is my Blood of the New Testament. Matt. xxvi. 26, 27, 28. And after this the invocation of the Holy Ghost, and the blessing the gifts, that is, the bread and wine which have been offered.
339. Why is this so essential?
Because at the moment of this act the bread and wine are changed, or transubstantiated, into the very Body of Christ, and into the very Blood of Christ.
340. How are we to understand the word transubstantiation T
In the exposition of the faith by the Eastern Patriarchs, it is said that the word transubstantiation is not to be taken to define the manner in which the bread and wine are changed into the Body and Blood of the Lord; for this none can understand but God; but only thus much is signified, that the bread truly, really, and substantially becomes the very true Body of the Lord, and the wine the very Blood of the Lord. In like manner John Damascene, treating of the Holy and Immaculate Mysteries of the Lord, writes thus: It is truly that Body, united with Godhead, which had its origin from the Holy Virgin; not as though that Body which ascended came down from heaven, but because the bread and wine themselves are changed into the Body and Blood of God. But if thou seekest after the manner how this is, let it suffice thee to be told that it is by the Holy Ghost; in like manner as, by the same Holy Ghost, the Lord formed flesh to himself, and in himself, from the Mother of God; nor know I aught more than this, that the Word of God is true, powerful, and almighty, but its manner of operation unsearchable. (J. Damasc. Theol. lib. iv. cap. 13, § 7.)
The Longer Catechism of The Orthodox, Catholic, Eastern Church • Pravoslavieto.com
Here is another one from the Confession of Dositheus:
Decree 17
We believe the All-holy Mystery of the Sacred Eucharist, which we have enumerated above, fourth in order, to be that which our Lord delivered in the night in which He gave Himself up for the life of the world. For taking bread, and blessing, He gave to His Holy Disciples and Apostles, saying: “Take, eat; This is My Body.” {Matthew 26:26} And taking the chalice, and giving thanks, He said: “Drink you all of It; This is My Blood, which for you is being poured out, for the remission of sins.” {Matthew 26:28} In the celebration of this we believe the Lord Jesus Christ to be present. He is not present typically, nor figuratively, nor by superabundant grace, as in the other Mysteries, nor by a bare presence, as some of the Fathers have said concerning Baptism, or by impanation, so that the Divinity of the Word is united to the set forth bread of the Eucharist hypostatically, as the followers of Luther most ignorantly and wretchedly suppose. But [he is present] truly and really, so that after the consecration of the bread and of the wine, the bread is transmuted, transubstantiated, converted and transformed into the true Body Itself of the Lord, Which was born in Bethlehem of the ever-Virgin, was baptized in the Jordan, suffered, was buried, rose again, was received up, sits at the right hand of the God and Father, and is to come again in the clouds of Heaven; and the wine is converted and transubstantiated into the true Blood Itself of the Lord, Which as He hung upon the Cross, was poured out for the life of the world. {John 6:51}
Further [we believe] that after the consecration of the bread and of the wine, there no longer remains the substance of the bread and of the wine, but the Body Itself and the Blood of the Lord, under the species and form of bread and wine; that is to say, under the accidents of the bread.
Further, that the all-pure Body Itself, and Blood of the Lord is imparted, and enters into the mouths and stomachs of the communicants, whether pious or impious. Nevertheless, they convey to the pious and worthy remission of sins and life eternal; but to the impious and unworthy involve condemnation and eternal punishment.
Further, that the Body and Blood of the Lord are severed and divided by the hands and teeth, though in accident only, that is, in the accidents of the bread and of the wine, under which they are visible and tangible, we do acknowledge; but in themselves to remain entirely unsevered and undivided. Wherefore the Catholic Church also says: “Broken and distributed is He That is broken, yet not severed; Which is ever eaten, yet never consumed, but sanctifying those that partake,” that is worthily.
Further, that in every part, or the smallest division of the transmuted bread and wine there is not a part of the Body and Blood of the Lord — for to say so were blasphemous and wicked — but the entire whole Lord Christ substantially, that is, with His Soul and Divinity, or perfect God and perfect man. So that though there may be many celebrations in the world at one and the same hour, there are not many Christs, or Bodies of Christ, but it is one and the same Christ that is truly and really present; and His one Body and His Blood is in all the several Churches of the Faithful; and this not because the Body of the Lord that is in the Heavens descends upon the Altars; but because the bread of the Prothesis* set forth in all the several Churches, being changed and transubstantiated, becomes, and is, after consecration, one and the same with That in the Heavens. For it is one Body of the Lord in many places, and not many; and therefore this Mystery is the greatest, and is spoken of as wonderful, and comprehensible by faith only, and not by the sophistries of man’s wisdom; whose vain and foolish curiosity in divine things our pious and God-delivered religion rejects.
[*Ed. Note: GK: prothesis, "setting forth," in Orthodox churches the liturgical act of preparing the bread and wine for the Divine Liturgy or Eucharist.]
Further, that the Body Itself of the Lord and the Blood That are in the Mystery of the Eucharist ought to be honored in the highest manner, and adored with latria [Gk: adoration or worship*]. For one is the adoration of the Holy Trinity, and of the Body and Blood of the Lord. Further, that it is a true and propitiatory Sacrifice offered for all Orthodox, living and dead; and for the benefit of all, as is set forth expressly in the prayers of the Mystery delivered to the Church by the Apostles, in accordance with the command they received of the Lord.
[Ed. Note: The Greek term latria refers to the highest form of adoration or worship and is directed only to God, as opposed to dulia, "veneration" of the saints, and hyperdulia, "highest veneration" of Mary.]
Further, that before Its use, immediately after the consecration, and after Its use, What is reserved in the Sacred Pixes* for the communion of those that are about to depart [i.e. the dying] is the true Body of the Lord, and not in the least different from it; so that before Its use after the consecration, in Its use, and after Its use, It is in all respects the true Body of the Lord.
[Ed. Note: Pixes: a container in which the consecrated bread for Communion is placed so that it can be taken to those who cannot leave home.]
Further, we believe that by the word “transubstantiation” the manner is not explained, by which the bread and wine are changed into the Body and Blood of the Lord, — for that is altogether incomprehensible and impossible, except by God Himself, and those who imagine to do so are involved in ignorance and impiety, — but that the bread and the wine are after the consecration, not typically, nor figuratively, nor by superabundant grace, nor by the communication or the presence of the Divinity alone of the Only-begotten, transmuted into the Body and Blood of the Lord; neither is any accident of the bread, or of the wine, by any conversion or alteration, changed into any accident of the Body and Blood of Christ, but truly, and really, and substantially, doth the bread become the true Body Itself of the Lord, and the wine the Blood Itself of the Lord, as is said above.
Further, that this Mystery of the Sacred Eucharist can be performed by none other, except only by an Orthodox Priest, who has received his priesthood from an Orthodox and Canonical Bishop, in accordance with the teaching of the Eastern Church. This is compendiously the doctrine, and true confession, and most ancient tradition of the Catholic Church concerning this Mystery; which must not be departed from in any way by such as would be Orthodox and who reject the novelties and profane vanities of heretics. But necessarily the tradition of the institution must be kept whole and unimpaired. For those that transgress, the Catholic Church of Christ rejects and anathematises.
The Confession of Dositheus (Eastern Orthodox)
Neither of these nor what I read in the Orthodox Faith on the oca.org website or posting on the Eucharist on the Orthodox Wiki site, have anything in them IMO that conflict the teachings of the Catholic Church.
So in all honesty I'm still at a loss on what is the difference between Catholic and Orthodox understanding on the Eucharist. I'm beginning to think there really isn't any, except we defined the fact as dogma, where the Orthodox churches have not done so. Even in this I'm not sure what the issue would be, as I think, correct me if I'm wrong, this teaching cannot change in the Orthodox Church any more than it can in the Catholic Church.