The aim of investigations was to understand the effect of application date (autumn and spring) of graminicides and their mixtures with adjuvant on efficacy of Elymus repens control and residue level in soil. Field experiments were carried out during 2007–2009 on arable field near Wrocław. Herbicides for E. repens control in winter oilseed rape (containing active substances such as: quizalofop-P-ethyl and fluazifop-P-buthyl) were applied alone at recommended dose and at reduced dose with adjuvant Atpolan Bio 80 EC, post emergence in the autumn and comparatively in the spring. In the experiments efficacy of E. repens control – per cent of weed control was evaluated and yield from each plot was calculated. Samples of soil were taken at harvest. All samples were analysed (herbicide residues) using the high-performance liquid chromatography (HPLC) with UV detection and GLC with MS detection. The phytotoxic effects of all used herbicides (alone and with adjuvant) on winter oilseed rape were not observed. Graminicides used in the autumn controlled E. repens in 94–99% and applied in the spring in 93–99%. The yield obtained from the herbicide objects (autumn and spring applications) was statistically higher in comparison with untreated objects. At the harvest time, residues of quizalofop amounted to: for autumn application 0.0031–0.0064 mg/kg, for spring application 0.0050–0.0098 mg/kg. Fluazifop residues amounted to: 0.0052–0.0108 and 0.0096–0.0194 mg/kg respectively. The residue active substances of herbicides, after spring application were higher than determined after autumn application. Application of herbicides with adjuvant allowed to reduce a herbicide dose (without lost of weed control efficacy) and residue level in the oil.