It is shown that oxygen-stabilized compounds Zr3NiOx (x=0.4, 0.6, 0.8, 1.0) interact with hydrogen at ambient temperature and pressure forming saturated hydrides with a filled Re3B-type structure. The hydrogen storage capacity decreases with increasing oxygen content from 6.65 H/f.u. for Zr3NiO0.4 down to 5.58 H/f.u. for Zr3NiO1.0. A slight decrease of the crystal lattice parameters of the parent compounds and a substantial increase of these parameters for the saturated hydrides were observed with increasing oxygen content. The partial hydrogen-induced lattice expansion, ΔV/at. H, increases from 2.333 Å3 for Zr3NiO0.4H6.65 to 3.047 Å3 for Zr3NiO1.0H5.58. Joint Rietveld refinement using X-ray and neutron powder diffraction data showed a distribution of deuterium atoms on similar positions as in oxygen-free Zr3FeDx and Zr3CoDx. The oxygen atoms move during deuteration from the octahedral site to one trigonal bi-pyramidal and two tetragonal interstices that are fully occupied in the saturated deuterides jointly by deuterium and oxygen. After deuterium desorption the oxygen atoms fully return to the initial octahedral site.