Mix ground turkey, feta, oregano, thyme and pepper in large bowl. Shape into 4 patties.
Heat oil in large nonstick skillet on medium heat until hot. Add patties; cook 4 to 5 minutes on each side or until burgers are cooked through (internal temperature of 165°F).
Mix yogurt and cumin in small bowl. Serve burgers on toasted rolls. Top each burger with 1 tablespoon of the yogurt mixture. Garnish with desired toppings.