Heat 1 tablespoon of the oil in a medium skillet over medium-high heat. Season the steak with 1/2 teaspoon salt and 1/2 teaspoon pepper and cook, 3 to 5 minutes per side for medium-rare. Transfer to a cutting board; let rest.
Wipe out the skillet and heat the remaining oil over medium heat. Add the mushrooms and cook, 3 minutes. Add the wine and cook until evaporated. Add the orzo and chicken broth and simmer until the broth is absorbed, about 10 minutes. Stir in the Parmesan, rosemary, and 1/4 teaspoon pepper.
Steam the broccoli rabe in a separate pot until tender, about 5 minutes, as the orzo cooks. Drizzle the rabe with the lemon juice. Divide among plates. Serve with the steak and "risotto."
Note: Orzo, a rice-shaped pasta, is a speedy stand-in for the Arborio rice traditionally used in risotto. Cooking orzo in broth instead of water intensifies its flavor.