‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌This study was conducted in winter season 2010-2011 in two Locatian Bashiqa/Tobzawh village (25 km) east of Mosul and at Hemidat/AL-Masiad village (20 km) west of Mosul. Both regions are located within the semi arid areas belt, it´s rainfall is about 300-450 mm/annually The study included Oats experiments at each site, to studying the effect of four nitrogen fertilizer levels (zero, 50, 75 and 100 kg N/ha,) and supplemental irrigation on straw yield and quality of five varieties of Oats (T, P ,M ,K and S) the experiment was carried out according to Randomized Complete Block Design (RCBD) with three replications.The most significant results, are the following All straw percentage of qualitative characters for straw surpass at 100kg N/ha their semiliriters at other ferlilizer levels with the exception of the percentage of crude fiber in the straw in both study sites.Oats varieties under this study differed form each other in all studied characters as well as both study sites.the characteristics percentage of qualitative characters for Oat straw were not significantly affected by supplementary irrigation at both study sites, except of the percentage of other extract in straw at AL-masia.