European countries are achieving higher levels of renewable energy penetration into their electrical grid (grid) systems than ever before. However, this comes with many challenges to the grid itself. If Europe hopes to continue growing its renewable energy industry, the grid must adapt to this growing penetration of variable sources of energy. The European grid is a network operated by numerous transmission system operators (TSOs) who have been working to coordinate their cross-border efforts at a regional level for many years, but some argue stronger coordination efforts are needed. The debate among industry stakeholders regarding the degree of cooperation, governance structures, and tools required present many challenges that necessitate multi-faceted solutions. This thesis assesses how cross-border transmission grid regionalization could be achieved to help European countries pool resources, reduce risk, and increase their security of supply from a regulatory standpoint. If European TSOs achieve stronger levels of regional cooperation this could facilitate an increase in the grids flexibility and enable higher penetration levels of renewable energy. The results conclude that Regional Security Coordinators (RSCs) are well suited to assume greater levels of responsibility to facilitate higher levels of cross-border electricity exchanges. RSCs are the most likely to garner the support necessary from TSOs for enhanced coordinating activities. Allowing RSC regions to fully implement all the tasks currently assigned to them is a necessary first step. Adhering to a strict timeline and enhancing oversight responsibilities of the Agency for the Cooperation of Energy Regulators will help shepherd efforts for enhanced cross-border cooperation among the TSOs. Continued utilization of platforms and algorithm development provide some of the tools needed by the TSOs for increased efficiencies. Harmonization of the borders for existing cooperative efforts, e.g. RSCs, Capacity Calculation Regions, and network development planning regions, would alleviate confusion and increase operational and overall grid efficiencies. Congestion rent is suggested as a means for financing the expansion of interconnection capacity, while establishing common methodologies for redispatching efforts could reduce the costs of this action. System Operation Guidelines, Electricity Balancing Guidelines, the Clean Energy Package represent the legal frameworks and the guidance necessary to build on for future cooperative efforts.