We study the photoinduced metastable stares in oxygen deficient YBa2Cu3Ox (x = 6.35 - 6.87). The states are identified by the intensity dependences of the CuO-chain resonance with photo irradiation and temperature. Below room temperature (RT) the CuO-chain resonance can be completely suppressed by irradiation with visible light polarized along the CuO chains, indicating photo-assisted oxygen ordering. Above RT the resonance intensity returns and saturates at T > 100 degrees C. This behavior exactly mirrors the temperature dependence of chain oxygen ordering observed by hard X-ray diffraction. The stability of the photo-induced state is in line with the reported persistent photo-induced superconductivity effects. (C) 2000 Elsevier Science B.V. All rights reserved.