In a large bowl, toss the first 5 ingredients (steaks through onion). Place the steaks and the onion on the grill and cook for 5 to 10 minutes on each side for the steaks, and 2 to 3 minutes on each side for the onions, until the steak and onion is cooked to desired level of doneness.
When steak and onion has cooled, cut both into bite sized pieces and divided into the lettuce leaves.
In a large bowl, mix the remaining 4 ingredients (avocados through garlic) with sea salt and freshly ground black pepper to taste. Spoon guacamole into wraps and serve.