Quoted from the webiste of Jewish Action (the OU’s magazine):
“Jewish Action, the quarterly magazine publication of the Orthodox Union, serves as a forum for a diversity of legitimate opinions within the spectrum of Orthodox Judaism.”
I think the same idea holds true for the OU in general. It was created and still exists to help the various needs of the entire spectrum of Orthdox Jews in America and beyond, and is staffed with such a diversity, so to call it a blanket term such as yeshivish or M.O. is in my opinion misleading. However, as a general gauge of “political” hashkafa and activism, I would say it does lean towards a more Modern Orthodox view. This, however, should not detract from its legitimacy in the eyes of more yeshivish or chassidish jews, but just the opposite: isn’t it beautiful that we can have at least one frum organization that turns away from the petty diferences between all frum, Orthodox Jews? That even chareidim eat foods with the hashgacha of a mosdos which includes the M.O.? I think it’s precisely that which makes the OU so globally recognized, unique and wonderful at what they do.