1. Preheat a grill with a medium-high heat for direct heat cooking.
2. Break the beef up in a large bowl and season with 11/2 teaspoons salt and 3/4 teaspoon pepper. Gently mix just to combine, then form into 4 (4 1/2-inch) patties, making a slight indentation in the center of each patty.
3. Brush the grill grate with oil. Evenly space the burgers on the grill and cook, turning once, until grill marks appear, 4 to 6 minutes total for medium. (Resist the urge to press down on the burger with a spatula as they cook.) Remove burgers from grill and let rest 1 to 2 minutes.
4. Brush cut side of buns lightly with oil and grill cut-side down until light golden brown, if desired. Put a burger on the bottom of each bun and top with lettuce, tomato, onion, ketchup, mustard, pickles and bun top. Serve with potato chips on the side, if desired.