The field of Human Computer Interaction still strives for a generalized model of visual search tasks (icon search, menu search, text search, label search, search through hypertext and feature recognition). The existing models of visual search, in spite of being impressive, are limited under certain perspectives due to lack of generality. The thesis tries to provide a holistic approach for the modeling of visual search tasks in graphical user interfaces from the Activity Theory (AT) perspective with the aim of rendering a theoretical bridge between HCI and Psychology. A detailed review of literature from the variegated discipline contributing to the study of Visual Search revealed the presence of gray areas, which can be partially addressed by the Activity Theory approach. The case study uses thinking aloud Protocol Analysis technique for analyzing the complex interaction of behavior, cognition and motor action, which manifest in these tasks. The results have been analyzed and possible modifications have been identified. Interestingly, it is observed that Activity Theory can provide substantial theoretical support to aid Usability Testing Techniques.