The productivity of sheep in Ethiopia is very low mainly due to a serious shortage of feedstuff. As a result, it is necessary to look for cheap locally available feedstuffs to sustain sheep production in the country. Non-conventional feeds like grass pea (Lathyrus sativus L.) hulls (GPH) could partly fill the gap in the feed supply, decrease competition for food between humans and animals and reduce feed cost. Therefore, this experiment was designed to evaluate effects of different proportions of grass pea hulls and concentrate mixture (CM) supplementation on feed intake, digestibility, and growth of Washera sheep fed finger millet straw (FMS) as a basal diet. Diets consisted FMS alone fed ad libitum (T1), 100% CM (T2), 30% GPH mixed with 70% CM (T3), 30% CM mixed with 70% GPH (T4), and 100% GPH (T5). For all treatments, FMS was fed ad libitum. Experimental sheep were arranged in a randomized complete block design and treatment feeds were assigned to the animals within a block. The results showed that FMS contained 5.5% CP and 68.9% NDF. The supplements contained 21%, 20%, 16% and 14% CP; and 36%, 43%, 52% and 59% NDF for T2, T3, T4 and T5, respectively. Supplementation improved (p resulted in the lowest ADG (p . While, animals in T1 lost a bodyweight of 5.6 g/day. As the proportion of GPH supplementation was greater than 30%, there was reduction (p T2 > T4 > T5. Therefore, from biological point of view as well as based on partial budget analysis, T3 was found to be recommendable for smallholder sheep producers.