T2K has published the first measurement of muon-neutrino disappearance by an off-axis experiment in Physical Review D at http://prd.aps.org/abstract/PRD/v85/i3/e031103.
The T2K beam is mostly composed of muon neutrinos, and 104 muon-neutrino events would have been expected in T2K’s far detector Super Kamiokande if there were no neutrino oscillations. However only 31 such events were observed, and it is believed that the deficit is due to oscillations from muon neutrinos to tau neutrinos. This result has been obtained from data taken from January 2010 – March 2011. Further details of this measurement are given in the list of T2K results, and the advantages of an off-axis experiment are explained on the About T2K page.