The efficiency of meat production with regard to kilogram of lamb weaned per kilogram metabolic mass of ewes at mating of six different Fl crossbred populations, viz. Finnish Landrace x Merino (FL x M), Border Leicester x Merino (BL x M), Bleu de Maine x Merino (BdM x M), Texel x Merino (T x M), Cheviot x Merino (C x M) and Merino Landsheep x Merino (ML x M), with their flock structures in equilibrium, were evaluated with each other over their lifetime. The FL x M was the most efficient cross followed by the T x M, BL x M, C x M, BdM x M and ML x M. Results indicate that size and other individual components of productivity are not reliable indicators of total production or efficiency of production.