A method of and apparatus for activating a ready-to-install heat activated adhesive for attaching a vehicle panel to a vehicle is disclosed which provides a "ready-to-install" panel assembly. The panel assembly includes first and second spaced apart surfaces, with the bead of heat activated adhesive provided on the second surface of the panel. The panel and bead are heated preferably by applying shortwave and longwave infrared radiation, with the shortwave infrared radiation being applied to an adhesive free side of the panel to heat the panel and, thereby, indirectly heat the bead of the heat activated adhesive. For example, where the window panel is such as a laminated windshield or side window or backlite comprising two glass sheets laminated with a polymer inner layer, such as plasticized polyvinyl butyral, or silicone or the like, it is preferable that the heat activation temperature of the adhesive be less than or equal to about 125.degree. C., more preferably less than or equal to about 115.degree. C., and most preferably less than or equal to about 105.degree. C. Also, when a ready-to-install adhesive is applied on or adjacent to a gasket such as a polyvinyl chloride (PVC) molding, a urethane molding, or the like, it is preferable that the heat activation temperature of the adhesive be about less than or equal to about 125.degree. C., more preferably less than or equal to about 115.degree. C., and most preferably less than or equal to about 105.degree. C. The longwave infrared radiation is applied to the adhesive side of the panel to directly heat the bead and thereby activate the adhesive. The apparatus includes a first heating component and a second heating component, with the first heating component including a source of shortwave infrared radiation, such as one or more lamps, which is adapted to heat the adhesive free side of the panel for indirectly heating the bead of adhesive. The second heating component includes a source of longwave radiation, for example a quartz emitter, which is applied the second side of the panel to directly heat the bead of adhesive.