The oxygen content in Pr 0 . 5 Ca 0 . 5 MnO 3 - z (PCMO)/YBa 2 Cu 3 O 7 - y (YBCO) bilayers was evaluated by means of non-Rutherford elastic resonance scattering, and the X-ray diffraction methods. Bilayers were fabricated on MgO(001) substrates by a pulsed laser deposition technique, in the ambient gas of 150 mTorr of O 2 +O 3 . An in situ annealing was performed in the same ambient as during deposition. The results revealed that a deposition of a thin PCMO overlayer causes a significant oxygen-deficiency in the YBCO underlayer, probably because the overlayer obstructs the passage of oxygen during the in situ annealing process. On the other hand, a post-annealing in 1 atm of O 2 gas completely recovers the oxygen-deficiency of YBCO underlayer.