Marks, thanks for joining the community. Wages paid thru a PEO will qualify as wages for QBI. Tony Nitti covered this in the proposed regs from IRS in November in JOA: https://www.journalofaccountancy.com/issues/2018/nov/irs-sec-199a-business-deduction.html 

"The proposed regulations ameliorate this concern by allowing W-2 wages paid by a taxpayer on behalf of a common law employer to be allocated to that common law employer. Thus, in the example above, the W-2 wages of the administrative entity would be allocated among the operating businesses based on the wages attributable to the common law employees of each business. This same rule will allow a business to receive an allocation of the W-2 wages paid through a professional employer organization."

Do make sure you review the facts and circumstances to determine who the true employer is. Are the "employees" ultimately under control of the client or the payroll company? These arrangements could go either way. Only if the facts and circumstances dictate the client here is truly the employer do the rules about third party payers apply. If it's a temp service, the employees may be employees of the third party company, and merely contractors to this client.

Good luck!