The effects of warm sheds on the performance of ewes and their lambs in winter are poorly understood. The aim of the present study was to examine the effects of traditional sheds (TS+grazing) and modified warm sheds (WS, no grazing) on the reproductive performance of ewes (as well as their liveweight) and their lambs during the winter-spring period. Cross-bred ewes (n≤120) were randomly assigned to two treatments, either TS (+ grazing) or WS (no grazing), during the winter-spring period of 2011, 2012 and 2013. This study was conducted on two adjacent farms with the two treatments applied on each. The ewes in the TS treatment were grazed continuously on pasture in the day and housed in traditional sheds each evening, whereas the ewes in the WS treatment were not grazed. The animals in each treatment were fed the same amount of feed. Ewes housed in the WS group had a higher liveweight and lower weight loss than ewes in the TS group (P≤0.004 and 0.005 respectively); over the 3 years, the weight loss of the ewes in both groups was worst in the first 2 months (December-January) compared with the later 2 months, and was significantly alleviated after the first year (2011; P<0.001). Lamb liveweight and gain were higher in the WS than TS treatment group (P<0.001) and the growth rates of the lambs increased continuously as shed temperatures increased. Lamb weight gain and birthweight increased significantly with increasing years of the experiment (P<0.001). There were more lambs born in the WS than in the TS groups (P≤0.020), with higher survival and twinning rates (P<0.05). As shed temperatures increased, lambing, survival and twinning rates increased continuously. Therefore, keeping livestock in warm sheds during the winter and spring period will lift animal productivity, leading to improved household incomes. Elimination of winter grazing will reduce damage to already degraded grasslands and will assist herders to develop more positive attitudes towards animal production enterprises.