The main difference between outsourced HR and a PEO is the relationship between the business and the vendor. A PEO is a co-employer, whereas an HRO (human resources outsourcing) company is a third-party provider. With outsourced HR, you’re simply using another company to handle specific human resources functions. But a PEO shares the responsibilities and obligations of the company. If you think outsourced HR is a better fit for your business, check out our reviews of the best HR outsourcing services.