Preheat oven to 200°C (180°fan-forced). Line a large baking tray with baking paper. Lightly spray tortillas with olive oil and bake for 6-8 minutes, turning halfway, until crisp. Set aside and break into pieces once cool.
Meanwhile, place beef in a large snap lock bag, add taco seasoning and rub to coat. Heat a lightly oiled char-grill pan over medium-high heat. Cook beef, in batches, for 1-2 minutes or until browned and cooked through. Set aside on a plate loosely covered with foil. In same pan, cook corn for 8-10 minutes or until lightly charred. Cool slightly and remove kernels with a sharp knife from cob.
Arrange lettuce, tomato, onion and capsicum on a platter. Top with beef, corn and tortilla crisps. Season, dollop with yoghurt, sprinkle with coriander and serve with lime wedges.
When cooking the meat wait at least 30 seconds before tossing or stir-frying. This gives the meat a chance to brown, giving it good colour and flavour - the second side will take a little less time to cook.
You can also slice beef rump, scotch fillet, sirloin or fillet of beef to make your own stir-fry strips.