A stabilized metal promoted aluminosilicate zeolite, useful in the selective catalytic reduction of nitrogen oxides with ammonia, having a silica to alumina mole ratio of at least 8 and less than 30 and an FT-IR absorption peak at 3781 plus or minus 2 cm.sup.-1 which stabilizes the zeolite against further dealumination such as under oxidizing and harsh hydrothermal conditions.