Mix meat with ¼ cup barbeque sauce and half of the package of onion soup mix. Form meat into 4 patties and brush each patty with olive oil. Cover and refrigerate for 1 hour to allow the flavors to develop.
Meanwhile, mix the remaining onion soup mix with the cream cheese, feta cheese, 1 tablespoon barbeque sauce, Tabasco sauce and sun-dried tomatoes. Cover and refrigerate for an hour, or up to 24 hours.
Just before grilling, remove both meat and spread from refrigerator.
Grill burgers over direct medium heat until the meat is no longer pink, 8 to 10 minutes, turning once halfway through grilling time.
Transfer burgers from grill to a clean platter.
Grill buns, if desired, after removing burgers.
Place the burger on bottom bun and top with a dollop of feta spread and red onion slivers. Replace top of buns and serve immediately.
Discover the perfect complement to lamb with Weber® Smoky & Thick Hickory BBQ Sauce.