Highlights: • Digestibility of weeds in olive groves and vineyards is comparable to forage species. • CWM of LDMC negatively correlates with weeds forage quality. • Disturbing agricultural practices like tillage increased the digestibility of weeds. • No relationship was found between weeds biomass and leaf traits nor pedoclimatic drivers. • Weeds in olive groves and vineyards represent a promising forage resource for livestock. Abstract: Biodiversity presence in perennial agroecosystems increases the provision of ecosystem services (ES). Weeds are known to deliver supporting or regulating services but their potential to provide provisioning services is less studied. Our study aims to quantify the potential of weeds to provide forage resources for livestock in two Mediterranean perennial agroecosystems: olive groves and vineyards. We used a trait-based approach to investigate the abiotic determinants of weed quality and quantity variations at both the species and community levels. We surveyed spontaneous vegetation in 16 vineyards and 16 olive groves in the French Mediterranean region with contrasting pedoclimatic conditions and agricultural practices, during spring and fall 2021. Four leaf traits were measured: Leaf Dry Matter Content (LDMC), Specific Leaf Area (SLA), Leaf Nitrogen Content (LNC) and leaf C/N ratio (Leaf C/N) and four forage potential indicators: dry matter digestibility (DMD), crude proteins (CP), neutral detergent fiber content (NDF) and aboveground biomass (AB). We found that DMD of perennial agroecosystems weeds is high (689 ± 116 g kg−1), and can be compared to those of forage species. Using linear mixed models and path analysis, we found that, at the community scale, LDMC is negatively linked to weed forage quality and that disturbing agricultural practices like tillage, increase weed forage quality. However we did not find any effect of agricultural practices or pedoclimate on weeds leaf traits or on weeds quantity. Our results revealed the potential of weeds as highly digestible forage resources for livestock. The long-term aim is to promote the integration of livestock in perennial cropping systems in order to reduce the use of herbicides and/or tillage and to diversify agricultural production.