The aim of this investigation was to quantify the scale of variation in the eating quality of two commercial beef muscles, M. longissimus dorsi (LD) and M. semimembranosus (Sm). Both the LD and Sm were excised from steers (n=81) and heifers (n=81) (classification grade O4H, O4L, R4H, R4L) within 48 h postmortem, vacuum packaged and stored at 4 °C until tested for eating quality at 14 days postmortem. Quality measurements analysed were: pH, Warner Bratzler shear force, sensory attributes, sarcomere length, Hunter L a b muscle and subcutaneous fat colour and chemical composition. Extent of variation in many eating quality measurements, with the exception of most sensory attributes and subcutaneous fat colour, depended on gender, classification grade or a combination of both. The LD was more variable than the Sm for most quality attributes and heifers were more variable than steers. No one carcass grade was more variable over all attributes analysed; with different grades causing higher or lower variances within certain attributes. Knowledge of the current scale of variation in the eating quality of beef is required by the meat industry, and is one that requires further research.