People might not agree with this but i say #7 1/2 shot would work well.
#6 shot would work great for pheasant but might be "overkill" for quail.
I was always told that #7 1/2 will work for everything in my area (ruffed grouse,wood cock, bobwhite quail and the occasional pheasant).

I have downed everything from squirrels to blue herons with 7 1/2's.
The blue herons are pretty big birds but the #7 1/2s with a modified choke at 30 yards made quick 1 shot kills out of them.
Don't tell the wardens .