Mastering proposal management is key to the very survival of organizations that capture and execute contracts to supply products or services. Systems engineering plays a central role in proposal management for complex systems by often leading the technical effort. This paper provides an alternative perspective to the existing acquisition-focused literature by examining proposal management from the supplier perspective. This paper identifies proposal stakeholders and defines objectives that can be used to evaluate success from each stakeholder's perspective. A high-level process model is identified that describes steps in the proposal process and the corresponding role of systems engineering. This paper also introduces a detailed process model for defining the proposed system solution. A more thorough understanding of proposal stakeholder roles, associated objectives, and the proposal process can help supplier organizations devise more effective strategies for responding to proposal opportunities.