The diet composition of Emperor PenguinAptenodytes forsterichicks was examined at Auster and Taylor Glacier colonies, near Australia's Mawson station, Antarctica, between hatching in mid‐winter and fledging in mid‐summer by “water‐offloading” adults. Chicks at both colonies were fed a similar suite of prey species. Crustaceans occurred in 82% of stomach samples at Auster and 87% of stomachs at Taylor Glacier and were heavily digested: their contribution to food mass could not be quantified. Fish, primarily bentho‐pelagic species, accounted for 52% by number and 55% by mass of chick diet at Auster, and squid formed the remainder. At Taylor Glacier the corresponding values were 27% by number and 31% by mass of fish and 73% by number and 69% by mass of squid. Of the 33 species or taxa identified, the fishTrematomus eulepidotusand the squidPsychroteuthis glacialisandAllu‐roteuthis antarcticusaccounted for 64% and 74% of the diets by mass at Auster and Taylor Glacier, respectively. The sizes of fish varied temporally but not in a linear manner from winter to summer. Adult penguins captured fish ranging in length from 60 mm (Pfeura‐gramma antarcticum) to 250 mm (T. eulepidotus) and squid (P.glacialis) from 19 to 280 mm in mantle length. The length‐frequency distribution ofP. glacialisshowed seasonal variation, with the size of squid increasing from winter to summer. The energy density of chick diet mix increased significantly pr