Before. The OCS application process just changed a bit... you do the security check as part of the initial application process, before your kit goes to the board for the professional reccomendation. Basically, its a requireent to pass the basic security clearance check to even be considered for OCS. Its the standard NSA background check that goes with a gov't security clearance.
You fill out the SF-86.. its amillion and a half pages long... goes into job history, drug use, police record, people you know, where you've lived, finacial history.. pretty much everything you can think of.
Hope that helps.
Cheers,
Bubba