1Heat gas or charcoal grill. In small bowl, mix 1/4 cup of the cheese, the olives and vinaigrette dressing; cover and refrigerate.
2In medium bowl, mix ground beef, oregano and remaining 1/4 cup of cheese. Shape into 8 equal patties.
3Place patties in grill basket; place on grill over medium heat. Cover grill; cook 8 to 10 minutes, turning once, until meat thermometer inserted in center of patties reads 160ºF.
4Place patties on bottom halves of buns. Top each with small spoonful of cheese mixture. Spread spoonful of hummus on top half of each bun; arrange bun halves over cheese mixture.