The multimodal Tongue Drive System (mTDS) is an assistive technology for people with tetraplegia that provides an alternative method to interact with a computer by combining tongue control, head gesture, and speech. This multimodality is designed to facilitate the completion of complex computer tasks (e.g. drag-and-drop) that cannot be easily performed by existing uni-modal assistive technologies. Previous studies with able-bodied participants showed promising performance of the mTDS on complex tasks when compared to other input methods such as keyboard and mouse. In this three-session pilot study, the primary objective is to show the feasibility of using mTDS to facilitate human-computer interactions by asking fourteen participants with tetraplegia to complete five computer access tasks with increased level of complexity: maze navigation, center-out tapping, playing bubble shooter and peg solitaire, and sending an email. Speed and accuracy are quantified by key metrics that are found to be generally increasing from the first to third session, indicating the potential existence of a learning phase that could result in improved performance over time.