[In reference to OCS for the Marines] You can do OCS while in college (Platoon Leaders Class), or after you obtain your Bachelor's Degree (Officer Candidate Course). With OCS you do not have to be enlisted beforehand or have done ROTC. As long as it is an accredited college you should be able to do OCS with a degree from there! Just as long as you qualify, obtain or are in the process of obtaining your Bachelor's Degree, and are accepted into the program you should be good to go!