Preheat the broiler. On a broiler pan, brush the steak on both sides with the oyster sauce and season with salt and pepper. Cook, turning once, for 10 minutes for medium-rare. Let rest for a few minutes, then thinly slice, reserving any juices.
Meanwhile, using a vegetable peeler, cut the cucumber into thin noodles, rotating to avoid the seeds; discard the seeds.
In a medium bowl, whisk together the lime juice, soy sauce and jalapeno. Add the cucumber, onion, bean sprouts and mint; toss to coat. Season with salt and pepper. Serve the salad topped with the steak and reserved juices.
