Future transplanting on oaks: replant prior to bud break as they swell.
About this stage.
They dont like root work while not dormant. That said, most trees will have some form of stress after transplant. Dont worry too much if they have a few days or even weeks of not looking at their best.
I transplanted this one in mid april right before bud break. It gave first flush about 2 weeks after. New buds are about to push second set of leaves now. Will remove unwanted branches after this second set of leave flush out, probably about mid june at solstice.
Btw, this is a Red Oak. Will take some closer pictures at home today.