Interaction of oxygen with the Mo(1 1 2) surface precovered by submonolayer beryllium films with various coverage degrees (θBe < 1) has been investigated by Auger electron spectroscopy, LEED and contact potential difference techniques. We have studied the effect of Be coverage degree on the oxygen adsorption kinetics, atomic structure and electronic properties of the O/Be/Mo(1 1 2) system. Contrary to the case of full-monolayer Be precoverage (θBe = 1), beryllium submonolayers can speed up the initial adsorption kinetics of oxygen by a factor of 10. The high sticking coefficient of oxygen on the Be/Mo(1 1 2) surface at θBe < 1 can be explained by the existence of areas on Mo(1 1 2) that are free of Be and provide fast oxygen adsorption, with O adatoms migrating further to the areas covered with Be (the spillover effect). The creation of beryllium oxide even on limited surface areas substantially decreases the oxygen sticking coefficient. This effect may originate from the surface deformation due to a structural misfit between the Be/O layer and the substrate. The coadsorbed Be/O layers with θBe < 1 modify the work function to values between those specific of the O/Be/Mo(1 1 2) systems with θBe = 0 and 1, which complies with the heterogeneous adlayer model.