Loosely shape the ground beef into 4 burgers, each about 3/4-inch thick, and sprinkle both sides with Montreal Steak Seasoning or salt and pepper. (Tip: Using your thumb, make a depression in the center of each hamburger for more even cooking.)
Cook the burgers on a grill preheated to high heat (you may also use a grill pan or skillet). Cook for 3 minutes, flip, and then cook for approximately 3 minutes more for medium-rare, 4 minutes more for medium.
On each salad plate, place a portion of the lettuce. Drizzle some of the dressing over the top, and then top with one of the burgers. Sprinkle with the tomatoes, onions, crumbled blue cheese, crumbled bacon, and optional avocado. Serve with additional dressing, as desired.