What letter comes next in the series M, B, O, D, Q, F, S?

Two separate runs are threaded together. The first, third, fifth and seventh terms are M, O, Q, S, each two places on from the one before. The second, fourth and sixth are B, D, F, likewise two places apart, and the missing term belongs to this second run, so it is F plus two, which is H. U is what the first run would give if the two runs were read as one; G and T come of moving one place on from F and from S respectively instead of two.