Abstract: Soybeans (Glycine max Merr) were dehulled and a batch was fermented before subjecting all to extrusion cooking. Firm unripe (UP) and firm ripe (RP) plantains were also milled and blended together with the soybeans in different proportion of 0, 25, 50, 75 and 100% respectively. The developed complements were evaluated for nutritional quality using albino rats as experimental animals. The values of Protein Efficiency Ratio (PER), Food Efficiency Ratio (FER), Net Protein Retention (NPR), Protein Retention Efficiency (PRE) were significantly different in both unripe and ripe plantain without additional protein source. There were negative growth rate in UP and RP relative to all the other blends. All organ weights of UP and some in RP were significantly different from others. There exist variation in the weight of organs in relation to various diets. Although there were no significant differences in the organs of rats fed with blends relative to those fed the casein diet. Non-fermented soybean compared favourably with other blends which is an indication that extrusion cooking could have reduced antinutritional factors in raw soybean.