I will be a first year student at MSUCOM and although I cannot give you an exact answer to your question, I hope I can offer you some advice that may help. We begin OMM in our first semester and continue throughout our first two years. Our third and fourth years are for clinical rotations, of course, but I do believe that you can opt to do OMM as an elective rotation. We have both lecture and lab on OMM (you have two hours/week in the lab but I was told that you should practice a lot more outside of class if you are to get really good at it) and there is ample time to use the lab and practice with your classmates. Also, MSUCOM has a student group called the UAAO (Undergraduate American Academy of Osteopathy) and they sponsor workshops, conventions, and allow members to take advanced courses in OMM (i.e. craniosacral therapy, etc.). I hope that this shed some light on your question. If I can be of any further help, please let me know.
OSU does 2 hours of lab a week along with 1 hour of lecture. I'm guessing most schools will be somewhere along that line. With so much basic science to cover there isn't enough hours in the week already.