The clinical Joint Cognitive System (JCS) includes the clinicians, electronic health record (EHR), and other infrastructure that maintain control in the system in the service of accomplishing clinical goals. The purpose of this study is to examine the relationship between levels of control using the COCOM model (scrambled, opportunistic, tactical, and strategic) and patterns of EHR use. Forty-five primary care visits were observed and audio-recorded. Each was coded for COCOM levels of control (IRR = 90%). Screen changes were recorded and time stamped (as either searching or entering). Levels of control were significantly related to preparation intensity (F (2,23) = 6.62; p=0.01), the number of screen changes involved in both searching (F (2,30) = 6.54; p=0.004), and entering information (F (2,22) = 9.26; p=0.001). Combined with the qualitative data, this pattern of EHR usage indicates that the system as designed may not provide effective cognitive support.