Read Dr. Kurt Marquart's "Liturgical Commonplaces" (pdf, 18 pgs, 915 KB) in the October 1978 issue of Concordia Theological Quarterly, published by Concordia Theological Seminary, Ft. Wayne, Ind.

Excerpts:

The notion of "worship" in popular Protestantism does not seem to suggest anything so formal as a church service. It is more likely to be associated with rousing choruses of "How Great Thou Art," either at a Billy Graham rally or in a rugged setting out of doors, preferably round a campfire, holding hands. Mawkish gimmickry of various kinds is marketed as making for "effective" worship. Church services themselves, however, are seen as rather drab and dreary on the whole. …

If the Means of Grace were mechanically interchangeable, rather than organically ordered, it would make sense to say: "Today we have Baptism and, therefore, we do not need Communion." Such an argument, however, is quite impossible. It should be equally impossible to argue: "As long as we have preaching regularly, and the Lord's Supper occasionally, the Means of Grace are in action, and all the rest is adiaphora." What must be seen is that in the Lutheran Confessions as in the New Testament the Eucharist is not an occasional extra, an exceptional additive for especially pious occasions, but a regular, central and constitutive feature of Christian worship. Preaching and the Sacrament belong together not anyhow, or helter-skelter, by statistical coincidence, but as mutually corresponding elements within one integrated whole.

Of the practice in apostolic and sub-apostolic times Oscar Cullmann has written in his book, Early Christian Worship, as follows:

The Lord's Supper is thus the basis and goal of every gathering. This corresponds to all that we have already determined about the place and time and basic character of the primitive Christian gathering. … Accordingly, it is not as though early Christianity had known three kinds of service, as we are in the habit of imagining, following the modern example: service of the Word and, alongside of it, Baptism and the Lord's Supper. It is rather so: in the early Church there are only these two celebrations or services—the common meal, within the framework of which proclamation of the Word has always a place, and Baptism ... The Lord's Supper is the natural climax towards which the service thus understood moves and without which it is unthinkable, since here Christ unites himself with his community as crucified and risen and makes it in this way one with himself, actually builds it up as his body (1 Cor. 10:17).