Yes, fall would be best. Water it thoroughly before you move it to make sure it is easier to dig in the area. Expect to go deep.

Get the new hole ready in advance so the plant doesn't sit out during the process.

Do I need to wait till leaf fall or just at the point they are showing leaf color?

I've always assumed that once a trees leaves have started to show color that it's already essentially dormant anyway, is that true?

I start transplanting red oak when leaves turn red,the tree is dormant enough.I hope you are prepared for one heck of a tap root on that oak.I have transplanted some oaks that size in the past,but you can do alot of damage to the roots digging a tree that size.
I would try to dig as much of the tap root as possible,if you have to cut the tap root use a sharp knife.
Mulch and water after planting,be sure to water all fall, until you either it gets enough rain or the ground starts to freeze.You do not want ground to wet before it freezes,this could cause root damage.

I think after 5 years its more than a seedling. I transplanted a true Northern Red Oak seedling in Mid-april and it just started pushing out its second flush of leaves! I think yours would be best transplanted in the fall. Just dig as deep and wide as possible. Good luck!

jqpublic

Wow your growing season is that far ahead of ours?In eastern WI the 2nd push of new growth on red oak will not come until mid to late june,if we have enough rain.
Maybe my advice about freezeing does'nt mean much.How deep does your ground freeze in zone7?

lp

What, you mean the ground actually still freezes somewhere? I can remember back years ago when it would freeze about 12" deep around here. Those days are gone. I bet it hasn't frozen more than a couple of inches in years.

Yep, no freeze here in Georgia that I know of!

It might freeze this winter if patterns continue...the last three months have shown a decisive trend towards the colder, that mimicks 1982-1985, which is the last time this happened...

Not here :( 98 today. Tomorrow 100...sunday 100!!