Twenty-four Najdi ram (BW 38.6±0.6 kg) were selected to evaluate the effect of feed restriction and frequency of feeding on plasma metabolites concentrations and production cost. Lambs were allotted randomly into three feeding groups. The first group was used as control and fed ad libitum (AL). The second and third group lambs were fed a restricted diet (R; at 0.85 of ad libitum) fed either once (R1m) or twice daily (R2m). Blood samples were collected on d 40, 47 and 55 for the determination of plasma metabolites and insulin concentrations. All lambs were slaughtered after 8 weeks. Results showed that AL feeding of lambs led to higher (P<0.05) BW, ADG, liver weight, internal tail fat weight and subcutaneous fat percentage than restricted fed groups. However, these parameters did not differ between both the restricted-fed (R1m and R2m) treatments. Cold carcass weight and percentages of lean and protein were not affected (P>0.05) by feed restriction Lambs fed twice daily (R2m) produced the least efficient lambs in feed: gain ratio in comparison with the other treatments. Plasma concentrations of urea, insulin, insulin-like growth factor-1 and calcium did not differ (P>0.05) between lambs subjected to once or twice feeding of 85% restricted diet, but were significantly lower than AL fed group. The AL-fed lambs had higher total costs while R1m showed the lowest total costs and highest net profit. It is suggested that once daily feeding at 0.85 of ad libitum level can be adopted as a nutritional practice for fattening lambs.