The effect of cicer milkvetch (Astragalus cicer L.) and sainfoin (Onobrychis viciifolia Scop.) on ruminal fermentation, methane production, and microbial nitrogen synthesis was assessed in two experiments. Experiment 1 analyzed two legumes, cicer milkvetch and sainfoin at two stages (vegetative and late flower) incubated with alfalfa (Medicago sativa) at five inclusion rates 0:100; 25:75, 50:50, 75:25, and 100:0 (as DM) in batch culture. Experiment 2 analyzed vegetative cicer milkvetch and alfalfa incubated in ratios of 25:75, 50:50, 75:25, and 100:0 (as DM) in continuous culture systems (RUSITEC). In batch culture, increased dry matter disappearance (DMD), and propionate percentage (%total), and reduced methane (mg·g⁻¹ DMD) occurred with vegetative cicer milkvetch inclusion. In RUSITEC, DMD linearly increased (P < 0.01), acetate:propionate ratio quadratically decreased, while ammonia (NH₃-N) concentration (P < 0.01) and butyrate percentage (%total) linearly decreased (P < 0.05) with increasing inclusion of cicer milkvetch. No differences were observed for methane (CH₄) production (mg·g⁻¹ DMD), or short chain fatty acid (SCFA) production (mmol·day⁻¹). Microbial nitrogen synthesis and efficiency of protein synthesis linearly increased (P < 0.05) with increased inclusion of cicer milkvetch. Results suggest cicer milkvetch may result in synchronicity of energy and nitrogen during rumen fermentation, which could enhance cattle production.