I have had Quail in with my Silver & Chinese Ring-Necked Pheasants in the past, & they were fine.
If the pheasant are in the pen first, I have had to acclimate them first by placing the quail in a cage, & then placing the cage w/quail inside the pen for 2-3 days.
First day, I open the door of the cage & see what happens when they venture out.
Last time, my juvenile silver male squeezed into the quail cage & nudged the rest of the quail that had stayed out, and claimed the cage as his! lol