A two-part grate assembly for a channeled drain trough. The grate assembly has a grate frame that receives a removable grate section. The grate frame has lugs with vertical projections extending therefrom that define securing recesses that assist in aligning and securing the grate frame atop a drain trough. Additionally, the present invention is directed to the use of an alignment bar that prevents the grate section from sliding out of operating position within the grate frame by restricting lateral movement of the grate section. Further, the present invention is directed to a method of providing a grate assembly for a channeled drain trough having a grate frame that is adapted to receive a removable grate section.