Laboratory work is critical in undergraduate engineering courses. It is used to integrate theory and practice. This demands that laboratory activities are synchronized with lectures to maximize their derivable learning outcomes, which are measurable through assessment. The typical high costs of the traditional engineering laboratory, which often militate against the synchronization of laboratory activities and lectures, have catalyzed the increased adoption of virtual laboratories in engineering laboratory education. The principles of assessment in the virtual learning environment are essentially the same as in the traditional learning environment, with the same requirements for fairness, reliability, and validity. This motivated the incorporation, in a Virtual Electronic Laboratory (VEL) environment, of a Bayesian network-based tool for the performance assessment of students' laboratory work in the environment. This paper details a description of the assessment tool, its verification, evaluation (as an assessment tool within the VEL environment), and application processes.