A modular sunroof frame assembly and method for a vehicle having a body structure is provided. The modular sunroof frame assembly is attachable to the body structure and includes right and left side rails, front and rear cross beams, and a plurality of corner attachment couplings. The right and left side rails have respective cross-sections throughout their length, front rail ends, and rear rail ends. The front and rear cross beams have respective cross-sections throughout their length, right beam ends, and left beam ends. The corner attachment couplings are fixed to the respective side rail end and to the respective cross beam end.