Everything on the OAT is covered by MCAT, however there may be a lot of MCAT portions that are more extensive that needed for OAT. Also, some topics covered on mcat are not needed for the oat.
Definitely Chad's videos for Chem/physics/ochem. Anything works for bio, you cold use your mcat books just cross check with the OAT guide to find out what topics you need to know.