When developing the owner’s cost estimates, the maturity of engineering deliverables has often used to define the class of estimate produced. This has long supported the standard estimate classification model but should not be the only parameter considered when defining the class of estimate in support of capital programs. There are several equally important aspects of the quality of the front end deliverables such as the accuracy of the engineering as well as the maturity of the project plan. The project plan needs to evolve at the same pace as the engineering deliverables and will likewise affect the level of schedule and cost estimate accuracy. Significant improvement in project cost and schedule outcomes are possible, depending on the details of the project plan and its relationship to specific project characteristics and risks. This paper will identify industry best practices for content of the project plan and the typical evolution of the plan through the project front end efforts and execution. Examples of owner project plans will be provided and as well as the impact various components of the plan have on the estimate/schedule accuracy and corresponding project risk.