Outsourcing consultants advise their clients on the best outsourcing options for various parts of their business, and which parts of their business would benefit most from outsourcing.
For example, having evaluated a business outsourcing consultants may advise a client firm that they would save money by outsourcing their payroll department and their IT department to third party firms. Outsourcing consultants would then usually evaluate outsourcing options, and work out the best third party firms to use for payroll and IT, in terms of price, efficiency, relevance to the client company, etc.