I agree with the comments above advising you to take the OAT when you feel adequately prepared. Many pre-health students (OD, MD, PharmD, DDS) choose to take their admissions test the summer/early fall after their junior year because that is generally when they have completed all the courses that have material covered on the exams and have ample time to study during the summer.
If you do this and you plan on applying at the same time, I would start working on your application now (personal statements, researching which schools you want to apply to, getting your list of activities together w/ appropriate descriptions, LOEs, etc.) so that when the cycle opens roughly at the end of June/early July, you'll be ready to submit your application even without your OAT scores. Most schools (with the exception of Berkeley) operate on rolling admissions meaning it's better to apply sooner than later so that your chances of securing a seat in the incoming class is higher.
When you submit your application, you don't need to have already taken the OAT, as long as you are schedule to take it before the school's specified date (usually Nov/Dec, I believe). OptomCAS gives you the chance to update your application once you submit, so you are able to submit your OAT scores/Fall grades after you've initially submitted.
I applied during this cycle and I messed up my timeline. I graduated from my undergrad institution in May and took 1-2 weeks as a break before hardcore studying for 3 months for my OAT, which I took early September (I gave myself that much time because I was also working 30 hours a week at my job lol). After I took my OAT, I procrastinated for a few months because I was unmotivated after 3 months of grueling studying and I was also finishing up prerequisites at a CC so I was still fairly busy, and so I had to haul ass on my applications for about a month (personal statements, supplemental essays, etc.) until I finally submitted just in time for Berkeley's deadline on Dec. 1st (I submitted my 4 other apps at the same time too). Nov 30th/Dec 1st were probably the most stressful days of my life LOL
Retrospectively, this is what I would have wanted my timeline to be after I graduated, but I think that as long as you HAVE a timeline and stick to it, you'll be fine 🙂 Good luck on your OAT and your applications!!
