Reverse applique
 

I am making a quilt in reverse applique blocks. I am wondering if I can machine around the sewn edges with a decorative stitch as part of the quilting before shadowing eyc.

Do you mean after hand sew it down? If so - you can add any decorative stitch you want - I am not sure you can sew with a decorative stitch to sew the edge down - it would be hard to keep the fabric turned under - at least for me.

I did mean after hand stitching not thought about before.

Some embroidery quilting software can be set up for reverse applique, so there is no reason that you couldn't do the whole thing by machine without an embroidery machine or software. If you are curious and can look at one of these machines, you will see how the software works and you can do the same on your machine.

If you look, there are probably old tutorials around from pre-embroidery machines. I have a cutwork one that any zigzag machine can do. Once you see how the design works, you can do the same manually. In fact, cutwork is similar in some ways to reverse applique.