i think i read earlier that you hadn't planned to use batting. if that's correct, then you don't really need to quilt it at all.
i don't remember ... is it a rag quilt, or will the seams be on the inside? if the seams are on the inside, you'll want to line it with someting to reduce lumpiness on the back (if that description makes sense). a nice, thick, prewashed flannel should do the trick. or a superthin cotton batting. (quilter's dream makes a really thin batting ... either "select" or "request" loft ... i can never remember which is the thinnest.)
anyhoooo ... do whatever you want to the top and lining. when it comes time to add the cowboys backing fabric, use a sturdy needle and thread that matches the fabric. take a small stitch that goes through the backing and lining. run the needle and thread under the backing as far as you can before you bring the needle back "up for air". then take another small stitch. repeat this, spacing them either evenly or randomly. the small stitches using matching thread should be all but invisible unless you look very closely.
i often do this when i want to make sure all the layers are secured to each other, but don't want the quilting stitches to detract attention from the piecing and or backing fabric. i will even go as far as to "blind quilt" the top to the batting first (hiding the stitches in the seam ditches) and then do the same to secure the backing to the other layers. on goes the binding when it's all done.
if you use a long needle, you'll be surprised how far apart you can place your stitches.