Make the salsa. Combine the onion, tomatoes, garlic and coriander in a bowl. Season with pepper, cover and chill for 30 minutes.
Heat the oil in a wok or large nonstick frying pan, add the onion and peppers and stir-fry for 3—4 minutes. Add the chicken, paprika, chilli powder, cumin and oregano and cook for a further 5 minutes or until the chicken is cooked through.
Meanwhile, wrap the tortillas in foil and warm them in the oven for 5 minutes or according to the instructions on the packet.
Spoon one-quarter of the chicken mixture into the centre of each tortilla, add a couple of tablespoons of salsa and some shredded lettuce. Roll up and serve warm.