Adding a small amount of Al to the well-known high entropy alloy (HEA), Al0.1CoCrFeNi, to form Al0.3CoCrFeNi, leads to the precipitation of highly refined ordered L12 precipitates, which are stable at 550 °C. However, the L12 precipitates (stoichiometry of (Ni,Cr)3(Al,Fe,Co)) are de-stabilized and replaced by coarser B2 precipitates on annealing at 700 °C. Contrastingly, in the Co-free, Al0.3CuCrFeNi2 high entropy alloy, the L12 precipitates are stable up to ~900 oC and exhibit a stoichiometry of (Ni,Cu)3(Al,Fe,Cr). Both these alloys were studied in great detail using insitu-synchrotron experiments, high resolution transmission electron microscopy and atom probe tomography. The results lead to interesting insights into the stability of ordered phases in HEAs as a function of composition and temperature. The effect of precipitation of ordered phases on the mechanical properties like micro-hardness and tensile strength is also analyzed. Tremendous increase in strength is observed up on precipitation of fine scaled coherent precipitates.