Preheat the grill: Fire up your Weber Spirit Grill to medium heat. Give it 10–15 minutes to preheat with the lid closed for even cooking.
Make the patties: In a bowl, mix ground beef with Hidden Valley Ranch seasoning. Gently form into 4 equal patties—don’t overwork the meat.
Mix the sauce: In a small bowl, whisk together all Big Ranch Sauce ingredients. Chill in the fridge while burgers cook.
Grill the burgers: Place patties directly on the grates and cook about 3–4 minutes per side, or until they reach your desired doneness. Add American cheese during the last minute and close the lid to melt.
Toast the buns: Slather buns with butter and place them cut-side down on the upper rack of your Weber Spirit. Flip once when you see grill marks—this gives a golden crunch without burning.
Assemble: Spread Big Ranch Sauce on both sides of the toasted buns. Layer with lettuce, sliced tomato, the cheesy patty, and pickles (if using). Serve hot and juicy!