Adequate planning is essential to successfully deliver a project. Construction site managers' "planning" efforts include various levels: (1) identifying the sequence and timing of activities; (2) scheduling and organizing the wherewithal to perform the job; (3) planning with other project teams to coordinate for shared resources and/or interaction; and (4) designing the production system. Although there are several studies on construction project planning and its outcomes, the research pertaining to the effect of the on-site planning during construction on the performance is very limited. This research, via a questionnaire-based survey, identifies the relationship between the site manager's effort on the 2nd and 3rd levels of planning and the work plan reliability (WPR), measured by the plan percent complete (PPC). The survey was distributed to site managers of general contractors and subcontractors in North Carolina, US. Eighty three useable survey responses were collected and classified based on management level, type of work, and project characteristics. Correlation analysis results show that there is a significant correlation between the efforts at the 3rd level of planning and the PPC average for the subcontractors. Results also show that the PPC variation decreases when more efforts are devoted on the 3rd level of planning.