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Residual feed intake (RFI) is the difference between the actual and expected feed intake of an animal based on its BW and growth rate over a specified period. The biological mechanisms underlying the variation in feed efficiency in animals with similar BW and growth rate are not well understood. This study determined the relationship of feedlot feed efficiency, performance, and feeding behavior with digestion and energy partitioning of 27 steers. The steers were selected from a total of 306 animals based on their RFI following feedlot tests at the University of Alberta Kinsella Research Station. Selected steers were ranked into high RFI (RFI >0.5 SD above the mean, n = 11), medium RFI (RFI ± 0.5 SD above and below the mean, n = 8), and low RFI (RFI <−0.5 SD below the mean, n = 8). The respective BW ± SD for the RFI groups were 495.6 ± 12.7, 529.1 ± 18.6, and 501.2 ± 15.5 kg. Digestibility and calorimetry …