I am not sure of how the Reformed Baptist partake in the Eucharist, but in Southern Baptist the Eucharist is something that is usually done once a quarter. It is purely symbolic to them and hold no sacramental value. It is respected but a Southern Baptist could go their whole life without ever taking it.
You can read chapter 30 in the 1689 London Baptist Confession of Faith to see the complete treatment of the Lord’s Supper. Interestingly, when the Southern Baptist Convention was organized in 1845, all of the delegates belonged to congregations and associations that had adopted the Philadelphia/Charleston Confession of Faith as their own. That confession’s chapter 32 appears to be identical to that of the 1689 London Baptist Confession of Faith used by Reformed Baptists, so I would be surprised if there is much difference in belief.
My experience is that monthly or quarterly observance is pretty standard among Reformed Baptist churches, just as it is in Southern Baptist churches (one source I read said there are regional differences, with SBC churches in the South tending to quarterly while those in the Northeast and West tending toward monthly observance). As to what it means, below are a few excerpts from the London/Philadelphia/Charleston Confessions:
Of the Lord’s Supper
The supper of the Lord Jesus, was instituted by Him, the same night wherein He was betrayed, to be observed in His churches unto the end of the world, for the perpetual remembrance, and showing forth the sacrifice of Himself in His death, confirmation of the faith of believers in all the benefits thereof, their spiritual nourishment and growth in Him, their further engagement in and to all duties which they owe unto Him; and to be a bond and pledge of their communion with Him, and with each other.
In this ordinance, Christ is not offered up to His Father, nor any real sacrifice made at all for remission of sin, of the quick or dead, but only a memorial of that one offering up of Himself by Himself, upon the cross, once for all; and a spiritual oblation of all possible praise unto God for the same. . .
The outward elements in this ordinance, duly set apart to the use ordained by Christ, have such relation to Him crucified, as that truly, although in terms used figuratively, they are sometimes called by the names of the things they represent, to wit, the body and blood of Christ, albeit in substance and nature, they still remain truly and only bread and wine, as they were before.
Worthy receivers outwardly partaking of the visible elements in this ordinance, do then also inwardly by faith, really and indeed, yet not carnally and corporally, but spiritually receive, and feed upon Christ crucified and all the benefits of His death: the body and blood of Christ being then not corporally, or carnally, but spiritually present to the faith of believers in that ordinance, as the elements themselves are to their outward senses.
So while it is “only a memorial” and an oblation of praise unto God, yet it is also something that provides “spiritual nourishment and growth” and “confirmation of the faith,” with the body and blood of Christ being “spiritually present to the faith of believers in that ordinance” such that “worthy receivers outwardly partaking of the visible elements in this ordinance, do then also inwardly by faith, really and indeed, yet not carnally and corporally, but spiritually receive, and feed upon Christ crucified and all the benefits of His death.”
To me, that’s not a rejection of the Eucharist, but maybe it is in the eyes of the Catholic Church. Would anything short of transubstantiation be considered a rejection of the Eucharist?
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