Because the OAT covers four genuinely different subjects -- three sciences, reading, physics, and math -- an unstructured study plan is one of the most common reasons students feel underprepared on test day, regardless of total hours spent studying. Here's a realistic, phase-by-phase approach.
Start with a baseline, and plan your application timing early
Before committing to a study schedule, take a full practice test under real timed conditions to see your actual starting point across all four sections. At the same time, remember that the OAT is applied for through ADA, similar to the DAT process -- work backward from your desired test date to figure out both when to apply and how much real study time you have before then.
Related: What to Expect on the OAT: Format, Scoring, and How to Prepare
The early phase: content review, weighted by real section proportions
Survey of the Natural Sciences carries the largest share of the exam by question count, followed by Reading Comprehension, Quantitative Reasoning, and Physics. Spend the bulk of your early study time on the science content -- Biology, General Chemistry, and Organic Chemistry -- while making sure Physics gets genuine, dedicated attention too, rather than being treated as an afterthought simply because it's the smallest of the four sections.
The middle phase: timed section practice
Once foundational review is underway, start practicing full, timed individual sections. Pacing is tight across the OAT, and it's a skill that only improves under real time pressure -- untimed review can leave you feeling more prepared than you actually are once the real clock is running.
The late phase: full-length, mixed-subject practice tests
In the weeks before your test date, shift toward full-length practice tests covering multiple sections in one sitting. Since these four genuinely different subjects are tested back to back, practicing the mental context-switching between Biology, Chemistry, Physics, Reading, and Math in one sitting builds a real stamina skill that isolated single-subject review doesn't.
The final stretch: light review and logistics
In your last week, shift to light, familiar review rather than new content, and confirm your Prometric appointment details, required ID, and testing-center location well in advance. Since the OAT is offered essentially year-round rather than on fixed dates, there's real scheduling flexibility -- but that also means there's no fallback "next test date" the way there is with a once-a-month national test, so don't leave logistics to the last minute.