Is it fair to say that Baptists have a liturgy? One distinctive of Baptists and many other congregational churches is that they have no prescribed method of worship. Unlike, say, an Episcopalian or a Roman Catholic, there is no prayer book and no guidance "from above" (in the earthly, not heavenly sense) as to the elements and order of a church worship service. Each congregation is free to explore and promulgate its own worship order.

That said, in effect, most Baptist services I've ever participated in or led have boiled down to:


A Welcome
Two or three songs, one of which might be a choir special
A single Bible reading
An offering
The Doxology
A prayer
A sermon
An altar call and a final hymn


Followed by coffee hour in truly progressive churches :)  Additionally, communion, to be held quarterly or monthly  is inserted between the sermon and the altar call.

While there is no strict order, I'm willing to bet that I've just described about 95% of them, and I've probably even got the order right in at least 80%.

Here's the question—is that a liturgy?  I know I'd reject that label, but is it fair to call it a liturgy? If it is, why do Baptists reject the claim. If not, what element is missing to call it such?
Yes and No

It is fair to say that Baptist services are liturgical, but I don't think I'd say that they have "a" liturgy (meaning that they generally adhere to a common liturgy).  

Many Baptist churches I've been to don't quite follow the formula you described.  Most follow it somewhat, but I think that to call it a common liturgy, it needs to be followed more closely than it actually is.

The best formula that I can come up with that describes every Baptist church I have been to is (in varied order):


Singing (varied number of songs)
Announcements
Prayer
Sermon


I feel that that is too generic to be called a liturgy, because:


The order varies from church to church.  
These are common elements, but these elements are practiced very differently in different churches (hymns versus rock bands, etc.)
Churches often have additional elements.


But that said, most Baptist churches are liturgical within themselves.  In other words, they don't necessarily follow the liturgies of other Baptist churches, but the pattern of a given Baptist church service changes very little from week-to-week.