This study takes as its basis a recognition that task-based learning is now recognized as having major benefits in promoting L2 learning, and how cognitive load affects speech production. In addition, there has been a recent examination of the impact of task complexity, real-world meaning, and the overall cognitive load needed to be expended by students. Different task types have been evaluated in terms of how they improve aspects of language. However, less consideration has been given to the effect on the cognitive load of different task types with the speech production processes (conceptualization, input, output identification, monitoring, and reformulations). Drawing on data collected from 112 participants (56 Native Speakers, 56 Non-Native Speakers) who completed a series of tests of varying complexity and were asked to evaluate on a rating scale, the level of mental effort expended. The results indicated that complexity increases mental effort and thus cognitive load, and that conceptualization appears to be one area where greater effort is required before being able to problems solving. Formulation comments suggest that there was a high level of hesitation, self-checking, and assessment as the level of task complexity increased. The implications for teaching and syllabus design are also considered.