Biogeography Based Optimization (BBO) is a new evolutionary algorithm for global optimization that was introduced in 2008. BBO is an application of biogeography to evolutionary algorithms. Biogeography is the study of the distribution of biodiversity over space and time. It aims to analyze where organisms live, and in what abundance. BBO has certain features in common with other population-based optimization methods. Like GA and PSO, BBO can share information between solutions. This makes BBO applicable to many of the same types of problems that GA and PSO are used for, including unimodal, multimodal and deceptive functions. This paper explains the methodology of application of BBO algorithm for the constrained task scheduling problems.