popa put it succinctly. The leadership of the OU (i.e. parent organization) is of MO officers and rabbis. And the OU is officially affiliated with the overtly MO RCA. In fact, the RCA was founded as the Rabbinical Council of the OU; later it merged with the Rabbinical Council of RIETS/YU to form the current RCA.
Sam: The kashrus division is jointly run by Rabbi Belsky and staffed with rabbis such as Rabbi Reisman.