Heat oil in a large non-stick frying pan or wok over high heat. Stir-fry beef, in batches, for 1-2 minutes or until well browned. Set aside on a plate loosely covered with foil. Reheat pan, add onion and garlic and stir-fry for 1 minute. Add remaining vegetables and stir-fry for 2-3 minutes. Add sauces and stir through.
Return beef and any juices to pan and toss to warm through. Sprinkle with nuts and toss to combine.
Serve beef stir-fry with rice. Sprinkle with green onions and chilli, if desired.