As a departure from the current state of practice, this study proposes to evaluate cost and schedule performance based on the early and accurate prediction of final outcomes, as opposed to the prevalent and reactive evaluation of final cost and schedule deviations at completion. Getting to know early in the delivery process the actual outcomes of a project enables project and corporate managers to undertake informed and proactive actions in a timely manner. To enable the assessment of predictability performance, a novel predictability index metric is proposed, investigated, and discussed. Based on the statistical analysis of data for 135 completed projects representing $29 billion in total installed costs, the predictability index measure is characterized and the major influencing factors on project predictability performance are unveiled. Also, actual case studies are discussed to illustrate the tangible benefits associated with the assessment of predictability performance to the project delivery process.