BACKGROUND: We hypothesized that alfalfa (ALF) or birdsfoot trefoil (BFT) eaten prior to a meal of endophyte-infected tall fescue (TF) or reed canarygrass (RCG) would provide benefits not possible when TF or RCG are eaten alone. In trial 1, four groups of five lambs were first offered ALF for 30 min followed by either TF or RCG for 3.5 h in a 2 × 2 factorial arrangement of a completely randomized design that included grass (TF or RCG) with or without ALF. Trial 2 was similar to trial 1 except we used a new group of lambs fed BFT. Forage, fecal and urine samples were collected and analyzed for dry matter intake and apparent digestibility of dry matter, energy (in Kcal), nitrogen and neutral detergent fiber. RESULTS: A meal of either ALF or BFT prior to eating TF or RCG caused lambs to eat more total dry matter and nitrogen (both in g d−1) and energy (in MJ d−1) than lambs fed only TF or RCG (P < 0.05). Lambs fed ALF slightly reduced intake of TF and RCG relative to unsupplemented animals. Lambs fed BFT ate slightly less RCG, but much more TF than unsupplemented animals (P < 0.10). Lambs ate much less BFT than ALF, but they were stimulated to eat TF to a greater degree by BFT than by ALF. CONCLUSIONS: The enhanced intake of TF by lambs provided BFT, as well as the greater nutrient intake by lambs fed legumes and grasses was likely due in part to complementary profiles of alkaloids, saponins, and tannins. Copyright © 2011 Society of Chemical Industry