In large bowl, combine ground beef and 1½ tablespoons (half the packet) Hidden Valley® Original Ranch® Dips Mix. Season with pepper. Use your hands to gently combine and form mixture into 4 loosely packed balls, about 2" thick. Refrigerate 30 minutes.
Mix together mayonnaise and remaining half dips mix in small bowl and set aside.
Heat oil in a large heavy-bottomed skillet (preferably cast-iron) over medium-high heat. When oil is smoking, add 2 patties and use back of spatula to flatten meat. Continue to cook and press until bottom side is deeply golden, about 3 minutes. Flip, season with salt and pepper, and top each with slice of cheese. Cook until cheese is melted, 1 minute more. Transfer cooked burgers to bottom buns and repeat with remaining patties.
Serve each burger with sliced tomato, red onion, pickles, lettuce, and ranch mayo. Season with pepper.