The invention relates to a method of preparing a thermoplastic vulcanizate comprising: a) melt processing a blend of thermoplastic polymer and vulcanizable elastomer in a multi-screw extruder having at least three intermeshing screws, wherein said screws have 3-170 mixing zones, and said extruder having a L/D ratio of 15-100, and a screw profile that has 3 to 17 meshes per L/D; b) adding at least one curing agent to the melt-processed blend of a) in at least one location in the first 46% of the length of said extruder, or adding at least one curing agent to the melt-processed blend of a) in a second extruder, so as to initiate curing of the blend: and, curing at least partially said elastomer by reactive melt processing. Improved processing, reaction kinetics and efficiencies are achieved, as well as thermoplastic vulcanizate products having decreased weight gain when placed in mineral oils.