Question
All the oak trees in our area have budded out for a few weeks now.  We have a 4" diameter laurel oak that was plant 1 yr ago in full sun.  Was beautiful and full of leafs.  Had a cold day (1) in early sept. and it lost all its leaves.  New buds came out in late Sept. 100+ (smaller leaves).  Now, the limbs are green and the buds are all small and tight with no sign of budding.
If the tree needs to be replaced I do not want to wait until it is really hot.  Current temps vary highs 50s to mid 80s, lows 40s to 70s.

Answer
It sounds like it was stressed during  planting and the cold spell stressed it further and it may just be slow in leaving out. If the limbs are green it sounds like it is still alive. But you are not sure you can check and see if the tree is still alive. Start at the end of a upper branch and scrape a small bit of bark off the twig --if the color under the bark is green then the branch is alive at this point on the branch. If the color is not green (brown) the branch is dead at this point on the branch. If dead continue down the branch scraping bark at interval (say 6 inches apart) and see what color is under the bark. If green stop scraping the branch is alive at this point on the branch If green is found wait and see if the tree will leaf out and when is dose you can then prune off the dead parts of the branches.
Sounds like the tree is alive just a slow "bloomer".