The structure and magnetic interactions of the triplon Bose-Einstein condensation candidates Ba₃Cr₂O₈ and Sr₃Cr₂O₈ have been studied thoroughly in the literature, but little is known about a possible triplon condensation in the corresponding solid solution Ba_3-xSr_xCr₂O₈. We have prepared various members of this solid solution and systematically examined their magnetic properties in high magnetic fields up to 60 T and at low temperatures down to 340 mK, by means of pulsed field and cantilever magnetometry. From these experiments for x Î {3, 2.9, 2.8, 2.7, 2.6, 2.5} , we find that the critical fields of Ba_3-xSr_xCr₂O₈ decrease monotonically with decreasing Sr content x. This change is in good agreement with the earlier reported variation of the magnetic interactions in these compounds.