The formability of coiled and annealed (O-temper) magnesium alloy sheet material in high temperature forming operations is sometimes adversely affected by small amounts of cold work introduced into the fine grained material during handling of the coil and unwinding it to obtain blank workpieces for hot stamping, hot blow forming, or the like. When necessary, the formability of the sheet material with regions of hard worked microstructure may be improved by predetermining a recovery heat treatment using small portions of the material in formability tests. The recovery heat treatment, determined for the specific coiled stock, may then be applied to the material of the coil as it is used in making vehicle body panels or the like.