Preheat a ridged chargrill or barbeque to moderately high. Rub the steaks with some vegetable oil and season with salt and pepper. Cook for a minute on each side or until cooked to your liking. You may need to do this in several batches. Transfer to a plate, cover loosely with foil and rest for 5 minutes.
Divide the steaks between the 4 rolls. Top with the coriander, lettuce and pickled vegetables. Add chilli, spring onion and soy sauce to taste.
For the pickled vegetables: Toss all of the ingredients together well and set aside to pickle for 30 minutes. Drain before serving.
There are an infinite number of filling options for these tasty Vietnamese rolls. Try shop-bought crispy shallots, mayonnaise, pickled radish, pate, chilli sauce, watercress or mint leaves.