An important aspect of Grid deployment is the allocation and activation of installed network capacity. Due to the data-intensive nature of Grid jobs, it is expected that optical transport networks will play an important role in Grid deployment. As Grids possibly consist of high numbers of resources and users, solving the network dimensioning problem using straightforward Integer Linear Programs (ILP) does not scale well with increasing number of jobs. Therefore, we propose the use of Divisible Load Theory (DLT) when modelling this OCS (with wavelength translation) dimensioning problem. We establish the suitability of this approach as an Optical Transport Network dimensioning tool in an excess load scenario for varying wavelength granularity, fiber/wavelength cost models, network topology, traffic demand asymmetry and Grid scheduling strategy.