I dont know, if the holes are big enough for the quails to escape. But I think the holes are big enough for some small predators to come in, so you could loose your quails this way. I would add some wire 10 mm x 10 mm.
That isn't a pen I would recommend for quail. Not only could the quail get out, but a snake, rat or mouse could get inside and kill the quail. If a oppossum, raccoon, cat or dog really wanted to get inside, I'm sure they could. Here is a link for ideas on cages for quail.