An investigation on weed management studies in onion (Allium cepa) was carried out during rabi seasons of 2006-07 and 2007-08 at CCS Haryana Agricultural University, Hisar. Early postemergence application (10 DAT) of oxadiargyl at 100 g/ha, pre-emergence application of oxadiargyl at 120 g/ha, oxyfluorfen at 250 g/ha, trifluralin at 1000 g/ha and pendimethalin at 1000 g/ha applied through spray supplemented with one hand weeding at 45 days after transplanting (DAT) resulted in significant reduction in population of Chenopodium album, Coronopus didymus, Chenopodium murale and Melilotus indica and higher bulb yield. Bioefficacy of all herbicides applied by spray method was more as compared to sand mix broadcast application