Personally, I do it all the time. I really can't bothered brooding different groups of quail all the time. I usually put the Bobwhite eggs in my incubator, wait 5 days, add the Coturnix eggs, and then they all hatch and brood together. It saves a lot of work. The incubation time is about 18 days, and 23 days, respectively. Coturnix grow twice as big as the Bobs each week. After about 4-5 weeks, depending on the weather, they are moved to grow out pens and separated. Never had a problem. I wouldn't try pushing it past the 5 week mark, because the Coturnix are ready to mate at 80 days, and can be aggressive toward the Bobs. They grow so much faster that they can easily kill them. The image below shows them together, an Italian Coturnix and a few Bobs hatched on the same day. The Coturnix is twice the size of the Bobs at three weeks and doesn't bother them. There are many more in there with them, just not in the pic. If it was reversed, The Bobs would eat him.
