Multiple ovulation and embryo transfer (MOET) is being used by the Scottish Agricultural College, Aberdeen to accelerate genetic change in the Simmental breed. The selection goal of the project is improving the efficiency of lean meat production. The factors in this goal are saleable meat (predicted from liveweight, fat depth and muscling score), food intake and calving difficulty (predicted from gestation length and birth weight). Success of the project depends on the generation of sufficient grade 1 embryos from selected donor heifers in a 12 week period following a performance test. Performance testing to assess beef characteristics can produce precociously fat heifers which may be detrimental to embryo production. The onset of puberty in heifers is also highly variable and influenced by many factors including body weight and nutrition. The objective of this study was to examine the relationship of superovulatory response to performance on test and age at the onset of puberty.