The influence of turbulence structure, parameterized by two point correlations, on the return-to-isotropy process is examined under controlled conditions. In order to determine the influence of structure, direct numerical simulations (DNS) of return-to-isotropy in homogeneous, anisotropic turbulence is performed on meshes of 5123 and 512x512x1024. Isotropic turbulence is generated by mechanical stirring (as in a wind tunnel). Anisotropy is then generated by one of four fundamentally different mean strains, axisymmetric expansion and contraction, plane strain, and pure rotation. Each strain produces very different structure within the turbulence. The influence on the return-to-isotropy process of the initial structure (parameterized by the two-point correlations) as well as Reynolds number and initial length scale, is characterized and used to calibrate the Oriented-Eddy Collision (OEC) turbulence model developed by Martell and Perot [1]. In addition, this data provides critical information for other turbulence models which incorporate turbulence structure.