A ceiling system which includes a substrate and securing members configured to engage a grid system to mount the substrate to the grid system. The securing members may include a mounting flange positioned with its bottom surface adjacent to the substrate. The mounting flange may be coupled to the substrate via fasteners. The securing members may further include a positioning member protruding from a top surface of the mounting flange and terminating in a distal edge. The positioning member may have a first side edge and a second side edge. The securing members may include a grid engagement member extending from the distal edge of the positioning member. The grid engagement member may be located centrally between the first and second side edges of the positioning member. The grid engagement member may have a U-shaped engagement portion configured to engage a grid member of the grid system.