The aim of this study was to determine whether processed karanj (Pongamia glabra) oil seed cake can be used as a supplement to partially replace soybean meal (SBM). Male lambs (n = 24) of uniform body weight (12.88 +/- 0.15 kg) were equally allotted at random to a SBM-based control (CON) and three test concentrate mixtures, containing detoxified solvent extracted karanj cake (SKC) using three processing methods: water washing (WW), 2.5% lime (LM) and 0.4% binder (BN) treatment. The processed SKC replaced 50% nitrogen of SBM of CON. The respective concentrate mixtures were fed along with ad libitum chaffed oat (Avena sativa) straw for 196 days. Dry matter intake was significantly (p < 0.01) lower on WW, LM and BN. Apparent digestibility coefficient of nutrients was comparable, except for total carbohydrates, which was significantly (p < 0.01) lower in LM and BN. Total gain, average daily gain and feed: gain ratio was comparable (p>> 0.05) between the CON and WW diets but significantly lower in LM and BN groups. Yield of greasy wool was lower (p < 0.05) in BN group. Comparable dry matter and nutrient (crude protein and total digestible nutrients) conversion efficiency was observed on CON and WW diet but the lambs on the LM and BN diets exhibited lower (p < 0.01) conversion efficiency. It is concluded that SKC after water washing could replace 50% of SBM nitrogen in protein supplementation.