Search-based Software Engineering stands for an important area of research which involves finding optimal solutions for software engineering problems according to a set of conflicting objectives. One of these problems is improving the software quality such as usability of user interfaces following the model-driven engineering (MDE) paradigm. Transforming models consist of a set of transformation rules that describe how a component from a source model can be transformed into one or several target models. Although alternative target models may be equivalent from the functional viewpoint, they may differ from the non-functional perspectives. Besides, they do not fulfil the same usability aspects. In this context, search-based algorithms aim to identify which alternative transformation will produce a highly-usable target model. This study addresses this issue by combining the power of model transformations engine and search-based techniques. Specifically, the proposed approach defines model transformation as a usability optimisation problem. It allows the search of the optimal alternative transformation from a large search space taking into account a set of required usability attributes and using an evolutionary algorithm.