I've had quail in an outside coop for several years now. I think my area does not have digging predators, or at least the ones I have, don't care enough to dig. As a result, I have been OK with a simple pen is that is basically a big wooden pen with chicken wire. Home made with a few 2x4s and smaller wood pieces.
No digging was needed, and the pen just simply sits on top of the ground. One precaution we did learn about after the first 2 incidents of a bird getting pulled through the 1" chicken wire holes was that we decided to use 1/4" hardware cloth on the bottom 1-2 feet of the pen. It took two times because we were unsure what really happened the first time and how to prevent it. (Now upon reading more from this site, it was likely a raccoon that pulls the bird through the 1" holes because the birds like to sleep near the edge of the coop even though they have all the entire coop to sleep in, far away from the edges of the coop).
It can be moved when needed but a few years ago, I learned that using straw helped in the sense of being able to keep them in the same spot, too. So now they have a fairly permanent spot where I clean out the straw every couple of months.
