The current study is part of a five-year multidisciplinary grant aiming to identify dietary, genotypic and metabolic factors affecting feed efficiency while additionally analyzing the effects of feed efficiency differences on feedlot performance and carcass characteristics. The current report summarizes the six groups of steers fed over five years. Feed efficiency was relatively repeatable from the growing to the finishing phase as steers classified as highly feed efficient during the growing phase remained more feed efficient than steers previously classified as mid and lowly feed efficient. Marbling differed due to feed efficiency classification but classification effects on other carcass traits were limited. Relative to other diet combinations, steers grown with roughage-based diets and finished with byproduct-based diets excelled in finishing phase growth rate, final bodyweight and hot carcass weight with no differences detected in feed conversion or marbling score.