Here's some ECF quotes that are relevant:
Athanasius, Letter 4
For perceiving this, and being assembled together with the Truth , they drew near, and said unto our Saviour, 'Where will You that we should make ready for You the Passover Matthew 26:17?' For no longer were these things to be done which belonged to Jerusalem which is beneath; neither there alone was the feast to be celebrated, but wherever God willed it to be. Now He willed it to be in every place, so that 'in every place incense and a sacrifice might be offered to Him Malachi 1:11.' For although, as in the historical account, in no other place might the feast of the Passover be kept save only in Jerusalem, yet when the things pertaining to that time were fulfilled, and those which belonged to shadows had passed away, and the preaching of the Gospel was about to extend everywhere; when indeed the disciples were spreading the feast in all places, they asked the Saviour, 'Where will You that we shall make ready?' The Saviour also, since He was changing the typical for the spiritual, promised them that they should no longer eat the flesh of a lamb, but His own, saying, 'Take, eat and drink; this is My body, and My blood. ' When we are thus nourished by these things, we also, my beloved, shall truly keep the feast of the Passover.
John of Damascus, An Exposition of the Orthodox Faith (Book IV)
John 6:48 For when He was about to take on Himself a voluntary death for our sakes, on the night on which He gave Himself up, He laid a new covenant on His holy disciples and apostles, and through them on all who believe in Him. In the upper chamber, then, of holy and illustrious Sion, after He had eaten the ancient Passover with His disciples and had fulfilled the ancient covenant, He washed His disciples' feet in token of the holy baptism. Then having broken bread He gave it to them saying, Take, eat, this is My body broken for you for the remission of sins. Likewise also He took the cup of wine and water and gave it to them saying, Drink ye all of it: for this is My blood, the blood of the New Testament which is shed for you for the remission of sins. This do ye in remembrance of Me. For as often as you eat this bread and drink this cup, you do show the death of the Son of man and confess His resurrection until He come.
Cyprian of Carthage, The Epistles of Cyprian, Epistle 75
For the faith of the sacred Scripture sets forth that the Church is not without, nor can be separated nor divided against itself, but maintains the unity of an inseparable and undivided house; since it is written of the sacrament of the passover, and of the lamb, which Lamb designated Christ: "In one house shall it be eaten: ye shall not carry forth the flesh abroad out of the house..
Hilary of Poitiers,On the Trinity (Book X)
That we may understand what was the cause of His sadness, let us see what precedes and follows this confession of sadness: for in the Passover supper our Lord completely signified the whole mystery of His Passion and our faith.
Gregory Nazianzen, St [325-389 AD], Oration 40
Again, He gave the Sacrament of the Passover to His Disciples in an upper chamber, and after supper, and one day before He suffered; but we celebrate it in Houses of Prayer, and before food,(g) and after His resurrection...
John Chrsytotom Homily 83 on the Gospel of Matthew
And why did they lead Him away there where they were all assembled? That they might do all things with consent of the chief priests. For he was then high priest, and all were waiting for Christ there, to such a degree did they spend the whole night, and give up their sleep for this object. For neither did they then eat the passover, but watched for this other purpose. For John, when he had said that "it was early," added, "they entered into the judgment hall, lest they should be defiled, but that they might eat the passover."
What must we say then? That they ate it on another day, and broke the law, on account of their eager desire about this murder. For Christ would not have transgressed as to the time of the passover, but they who were daring all things, and trampling under foot a thousand laws. For since they were exceedingly boiling with rage, and having often attempted to seize Him, had not been able; having then taken Him unexpectedly, they chose even to pass by the passover, for the sake of satiating their murderous lust.
For after having shown His own strength, then at once He yielded Himself. But John says, that even to the very moment He continued to reprove him, saying, Judas, do you betray the Son of Man with a kiss? Luke 22:48 Are you not ashamed even of the form of the betrayal? Says He. Nevertheless, forasmuch as not even this checked him, He submitted to be kissed, and gave Himself up willingly; and they laid their hands on Him, and seized Him that night on which they ate the passover, to such a degree did they boil with rage, and were mad.
John Chrsytotom Homily 83 on the Gospel of John
But what is, 'That they might eat the Passover?' For He had done this on the first day of unleavened bread. Either he calls the whole feast the Passover, or means, that they were then keeping the Passover, while He delivered it to His followers one day sooner, reserving His own Sacrifice for the Preparation-day, when also of old the Passover was celebrated.
But how, if they were eating the passover, did they eat it contrary to the law? For they should not have eaten it, sitting down to their meat.What then can be said? That after eating it, they then sat down to the banquet.
Augustine
Letter 36 (A.D. 396)
One day having intervened -- on the evening of which, at the close, namely, of the day which we call the fifth day of the week, the Lord ate the passover with His disciples -- He was thereafter betrayed on the night which belonged to the sixth day of the week, the day (as is everywhere known) of His passion...
Letter 55 (A.D. 400)
" And the same evangelist who records that saying is to be understood as desiring to give emphatic testimony to this, when, speaking of the Lord as about to celebrate with His disciples the passover, at which He instituted the sacramental supper, he says, "When Jesus knew that His hour was come, that He should depart from this world unto the Father
Clement of Alexandria
Accordingly, in the years gone by, Jesus went to eat the passover sacrificed by the Jews, keeping the feast. But when he had preached He who was the Passover, the Lamb of God, led as a sheep to the slaughter, presently taught His disciples the mystery of the type on the thirteenth day, on which also they inquired, "Where wilt Thou that we prepare for Thee to eat the passover?" It was on this day, then, that both the consecration of the unleavened bread and the preparation for the feast took place.
Origen
He asserts, moreover, that "the body of a god is not nourished with such food (as was that of Jesus)," since he is able to prove from. the Gospel narratives both that He partook of food, and food of a particular kind. Well, be it so. Let him assert that He ate the passover with His disciples, when He not only used the words, "With desire have I desired to eat this passover with you," but also actually partook of the same.