Abstract: An improved tool tray support assembly comprises a center section, opposed extensible lateral support members and end support assemblies. The end support assemblies fit onto end sections of the lateral support members, and support the assembly on opposed edges of an engine compartment of a motor vehicle. The lateral support members slide within the center section and can be locked at any desired position to adjust the spacing of the end supports to accommodate various engine compartments. The angular orientation of the center section can be varied by adjustment of the position of the lateral support members with respect to the end supports. Tool trays of standard dimensions fit between the opposed lateral rails of the support member to enable convenient storage of small tools and parts. The tool tray assembly may also be supported beneath a vehicle service lift or the like, and the tool trays may be supported by brackets on wheeled stools for increased flexibility in their use.