Sainfoin (Onobrychis viciifolia) is a temperate legume plant containing condensed tannins (CT), which are polyphenols able to bind proteins and thus reduce protein degradation in the rumen. This study focused on five dates in the first growth cycle to track the time-course evolution of phenological stage, morphological composition (leaf proportions), nitrogen content and organic matter digestibility (OMd) of three varieties of sainfoin (Esparcette, Ambra, Villahoz) compared with a tannin-free legume, lucerne (var. Aubigny). Although sainfoin developed earlier than lucerne, its digestibility was higher or close to that of lucerne. Among the three varieties of sainfoin, Villahoz had the highest OMd and N content and the lowest CT content. Although nitrogen content was lower in sainfoin than lucerne, the tannins contained in sainfoin lead to similar nitrogen values. These results highlight sainfoin as a valuable alternative legume forage to lucerne.