If an Officer resigns their commission at the end of their contract and leave the military, can they rejoin at a later date as officers?

BLUF: Yes, it can be done. It will take paperwork and contacting someone in Officer Strength Management.

Below is a link to an RP post about this topic:

https://www.rallypoint.com/answers/can-an-officer-s-commission-be-later-reinstated-when-the-officer-initially-resigned-the-commission-and-received-an-honorable-discharge

Possible, but no cakewalk- if you quit once, why should they spend a fortune and take another chance?

Obviously things are different for NG vs. Reserve vs. Active. That said, I do have experience in the later two sides with the answer being "it depends". For designators which are heavy on pedigree requirements, doctors etc. typically don't lose a step. In my engineering designator, I was a Reviewing Officer who'd determine if the individual was worth while bringing back in. The percentage allowed to come back tended to run about 25% because the reason they resigned was also reflected in their evaluations in one form or another. Then there is where in the zone you're placed. We'd start an Ex O-3 back with zero time in grade and full time in service. That would allow for performance and paper to match for zoning into O-4 and to make sure the officer could achieve ongoing pedigree requirements. Possible? Yes. But you have to work for it.