In this paper, we examine the unfolding process of newcomers’ learning in routine dynamics. Mainly viewed as cognitive schemas, previous research has provided evidence for the storage of routines as procedural memory. As mindful accomplishments, studies in routine dynamics have shown that learning can be an ongoing process, as individuals adapt their performances and pattern routines accordingly. Nonetheless, little is known about how learning takes place when routines are not to change but the organizational members performing them are. We address the questions of how organizational members learn to competently perform routines, and how this learning process shapes routine dynamics, through a four-year ethnographic study of an emergency room at a university hospital characterized by high rates of personnel turnover. We find that, in learning how to perform routines, newcomers draw on four learning practices (stunt performing, virtual performing, collegial learning, and self learning), which result in routine stretching. Our findings lead to a theoretical framework which outlines the learning process newcomers go through and its influence on routine dynamics. Our study contributes to research on routines by articulating the learning process organizational members undergo in becoming skillful at performing routines and how this enables new and old routine participants to align their lines of actions in reproducing routines as patterns-in-variety."