It depends on how thick your boned breasts are. Assuming a max of about 1/2 inch, I would go pretty hot, enough to sear the outside in about 30 seconds on each side, turn down heat slightly and finish for one or maybe two minutes. Take out the quail, and deglaze the pan with a couple ounces of white wine, or other liquid, for sauce. That should result in fairly rare, but still moist, meat. Given all the variables of "hot", I would add that as soon at the breast starts to feel firm, it's time to stop.
Best of luck
