When should I start MCAT prep course?

So I need some advice.

Pre-med Classes finished:
3 quarters of general BIO (3 A's)
3 quarters of general Physics (+more, Physics major) (2 B+'s, 1 B-)
3 quarters of general CHEM (3 A's)
1 quarters of organic CHEM (currently in my 2nd quarter) (B+)
highschool AP transfer credit for psychology

Upcoming classes:
Spring quarter(2016): sociology, and last quarter of ochem
Fall(2016): biochem, genetics, microbiology
Winter(2017) Physiology

My question is, when should I plan on taking the MCAT?...

When should I start MCAT prep course?