The CEO of Whataburger is retiring after 20 years at the San Antonio-based restaurant chain, and a recent addition to its executive team with stints at Starbucks and McDonald’s is set to take over. Current CEO Ed Nelson will step down at year’s end, allowing Chief Operating Officer Debbie Stroud to take the top slot, according to officials with the South Texas-born burger institution. Nelson joined Whataburger two decades ago as controller and played a role in improving the company’s debt structure and financing, according to his LinkedIn.