Technical Abstract: Metabolites involved in the metabolic adaptation to negative energy balance may have the potential to regulate timing of reproductive success. Therefore, the objective of this 4-yr study was to determine the association of serum metabolites, cow BW, BCS, and calf performance on conception date in 2- and 3-yr-old beef cows (n = 381) grazing native range at the Fort Keogh Livestock and Range Research Laboratory. Cows were classified by conception date in a 55 ± 2 d breeding season as early conception (EC; conceived in first 15 d of breeding) or late conception (LC; conceived during the remaining breeding season). Date of conception was calculated from the following year calving date. Blood samples were collected 30 ± 1 d prior to calving and 14 ± 1 d prior to breeding for analysis of serum IGF-I and '-hydroxybutyrate (BHB) concentrations. Conception date for EC cows were 33 d earlier (P < 0.01) than LC cows. Sampling time did not interact (P > 0.10) with conception date classification group for either serum metabolite. Cow age × conception date interaction (P = 0.04) occurred for serum BHB concentrations. Serum BHB concentrations were similar (P > 0.10) for 2-yr-old cows relative to their conception date classification. However, serum BHB concentrations were greater (P = 0.05) for LC rather than EC in 3-yr-old cows. Serum IGF-I concentrations were greater (P < 0.01) for EC cows relative to LC cows. Body condition score and cow BW were not different (P > 0.43) at calving and breeding between EC and LC cows. Calf birth BW was not different (P = 0.25) for EC and LC cows. However, calf weaning (205-d) BW was greater (P < 0.01) for LC cows relative to EC cows, indicating a difference in milk production. This study indicates that serum BHB and IGF-I concentrations may be practical indicators of conception date prior to breeding in young beef cows grazing native range.