Proanthocyanidins (PAs) in sainfoin (Onobrychis viciifolia Scop.) are of interest to ameliorate the sustainability of livestock production. However, sainfoin forage yield and PA concentrations, as well as their composition, require optimization. Individual plants of 27 sainfoin accessions from four continents were analyzed with LC-ESI-QqQ-MS/MS for PA concentrations and simple phenolic compounds. Large variability existed in PA concentrations (23.0−47.5 mg g−1 leaf dry matter (DM)), share of prodelphinidins (79−96%), and mean degree of polymerization (11−14) among, but also within, accessions. PAs were mainly located in leaves (26.8 mg g−1 DM), whereas stems had less PAs (7.8 mg g−1 DM). Overall, high-yielding plants had lower PA leaf concentrations (R2 = 0.16, P < 0.001) and fewer leaves (R2 = 0.66, P < 0.001). However, the results show that these two trade-offs between yield and bioactive PAs can be overcome. KEYWORDS: