The paper presents the results of study of 25 best accessions of grass pea from VIR collection previously selected by the complex of the agronomic traits (Burlyaeva et al., 2012). The plants of the studied sample reproduced in different ecological and geographical conditions (Ukraine, 2013 and Leningrad region, 2012-2013). The variability of the protein and dry matter content in green mass have been studied. The values of the traits varied depending on the growing conditions for protein content – from 10.0% to 27,9%, for a dry matter – from 17,6% to 28,8%. The values of genotypic variance (CV) fluctuated from year to year for the protein content from 5,63% to 11,57%, for dry matter content from 7,33% to 9,35%. The proportion of the variability due to environmental factors and the interaction "genotype – environment"(CV), was detected for protein and dry matter, 10,09% and 8,89% respectively. Multivariate analysis of variance revealed that between protein and dry matter in the green mass and eco-geographical origin of genotypes there were no significant relationships. The variability of protein content in the green mass is largely dependent on the weather conditions (the proportion of the influence of the environment (η2) – 89,5%). Variability of dry matter content was less correlated with meteorological conditions (η2 = 11,7%). Evaluation of adaptive capacity and stability of genotypes according to the method A.V. Kilchevsky and L.V. Khotyleva (1985) made it possible to identify biochemical parameters the general (GGA) and specific (SAA) adaptive ability and stability of genotypes. GGA of genotypes in protein content fluctuated from -2,02 to 1,52, SAA from 14,6 to 21,8, in dry matter GGA ranged from – 4,45 to 2,23, and SAA from 8,42 to 12,90. As a result of the research it was shown the comparability of results obtained in the calculation of the stability of the genotype with the help of CV (coefficient of variation) and Sgi (relative stability of genotypes). So, the studied accessions obtaining the high value of agronomic traits also revealed high overall adaptive capacity and stability with high protein content (k-900, k-712, k-841) as well as high dry matter content (k-42, k-47, k-292) were revealed.