Proposal engineers develop and review contract bids for projects based on what the client needs. As a proposal engineer, you gather supporting documentation to make the proposal more competitive. You determine costs and timelines, and may outline a variety of factors that may increase or decrease them. Projects may range from large building construction to software development. Proposal engineers must have extensive knowledge of the industry in which they work; they collaborate with sales and design staff to ensure the contract proposal accurately reflects what the company can provide the client. Some proposal engineers work for a consulting firm and are hired by companies, while others work in the sales department of a company.