The shape of the dose-response curve (DRC) of the OSL signal in the high dose range limits the dating range. No agreement between natural and laboratory DRC for doses close to saturation is indicated in OSL dating using quartz. The natural curve rises slower to a saturation level that is clearly lower than the saturation level of the laboratory curve. The latter is often a sum of a single saturating exponential function and a linear increase up to several kGy. Previous studies have shown that by changing the procedure for the DRC determining, one can extend the range of agreement of the curves, obtaining a slower growth of the laboratory curve. Processes occurring in the sample during the DRC determination procedure strongly influence its shape. The present study concerns the dependency of the DRC shape for doses close to saturation on the concentrations and parameters of centres participating in the OSL process. The research is for a model involving two OSL traps, one deep trap not emptied during the construction of the DRC and two recombination centres. One simulated the entire procedure of the DRC determination with OSL sensitivity control. Studies show that the DRC shape in the high dose range is primarily due to the competition of recombination centres.