i took the mcat w/o the 3rd quarter of o-chem and the bio section still went pretty well. i think 2 quarters is enough. and honestly, you need to know about 1/100 of what you learn in the first 2 quarters. you just need to understand the basic concept(i.e. general reactions that aldehydes/ketones undergo) but no crazy mechanisms! good luck.
I took the MCAT right after 3 quarter of o-chem and scored double digits on bio....but to be honest with you I didn't think that quarter of o-chem really helped...just focus on your sN1/2 E1/2 reactions that spectroscopy sh-t and you'll be fine....I guess it kind of helped that I tutored o-chem too 🙂
I took the MCAT after 130a and 130AL. I scored double digits on the bio (and I was slacking off in that section because I was terrified of the physics....)
Just to reiterate what ucla2001 said, I used the Berkeley Review and I took O Chem in 1994(!). I did fine, but I did have to study alot to feel "comfortable" before the MCAT.