We report the effect of start epi-material variability on the performance of double-recessed power pseudomorphic high electron mobility transistors. Variation in channel-recess depth, which is related to variation in the start material, is critically linked to rf performance of monolithic microwave and millimeter wave integrated circuit high power amplifiers. For high yield, it is important to control the channel recess, which in turn has implications on acceptable variation in epi-material. Design tweaks can relax channel-recess tolerance limits, but it is still important to account for material variation.