Cognitive load is a relevant phenomenon experienced by novice teachers moment-to-moment in complex classroom environments. Teachers learning to teach within the classroom daily encounter mental workload, but the latter has played little part in learning design for teachers, although other professions demanding complex performanes have made use of Cognitive Load Theory and Cognitive Task Analysis for learning design and for the reduction of cognitive load. Exploration of the lived experience of cognitive load was the focus of this study. The purpose of this phenomenological study was to describe the limits of mental capacity and the mental liberty experienced by teachers who undergo different levels and types of cognitive load. The researcher exposed the multiple directions of awareness that result from looking at learning to teach through this lens, how teachers perceive the availability and immediacy of mental resources, and reconstruct lived experiences in the moment of classroom teaching. The consequenes of cognitive load, the resulting experiences from having undergone it, are explored as automaticity and higher levels of load reveal various levels and types of learning. New directions of learning design for teachers based on expertise transfer and complex learning models are proposed. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]