Combine hummus, lemon juice, parsley, and pepper in small saucepan. Cook over medium heat, stirring constantly, about 8 minutes or until sauce is heated through. Set aside and keep warm.
Combine ground beef and seasoning mix in large bowl. Mix thoroughly. Shape into four ½-inch-thick burgers.
Heat large nonstick skillet over medium heat. Cook burgers, 5–6 minutes. Turn and cook 5–6 minutes, or until no longer pink in center (burgers should reach 165°F). Line bottom of each bun with lettuce, tomato, and cucumber slices. Top with burger and 2 tablespoons of hummus sauce. Serve with remaining sauce and garnish with carrot and celery sticks, if desired.