The European Corporate Sustainability Framework (ECSF) is, among other concepts, based on a phase-wise development approach as described by Clare Graves' Levels of Existence Theory. As much as corporate sustainability has a sequence of adequate interpretations, aligned with each development level, also the notion of business excellence can be defined at multiple levels, as this paper demonstrates. Furthermore, the authors analyze the current EFQM Excellence Model for particular biases towards various development levels and suggest a new and innovative two-step approach (...) to assessing organizational performance with respect to organizational excellence (OE) and corporate sustainability. According to the organization's ambition, the assessment is either limited to a shareholder approach, mainly focusing at optimal usage of resources, or it also includes an additional assessment format based on the stakeholder approach, with specific reference to the organization's performance on the financial, social and ecological bottom line. This paper demonstrates the need and feasibility of an EFQM-Based assessment tool with a combined focus on corporate sustainability and OE. (shrink)