Score both sides of the steak in diamond pattern by carefully making 1/8" deep diagonal cuts with a sharp knife at 1" intervals.
Rub half of the garlic and 2 teaspoons of the rosemary into both sides of meat and season with salt and pepper.
Heat a tablespoon of the oil in a large non-stick skillet over medium heat.
Add steak and cook, turning once, about 4 minutes per side for medium rare (add more time if you prefer). Transfer to a plate and loosely cover with foil to keep warm.
Heat remaining oil in the same skillet. Add onion and cook stirring often, for 2 minutes. Add remaining garlic and cook, stirring constantly, until fragrant, about 30 seconds.
Add asparagus and mushrooms and cook, stirring often, until asparagus is crisp and tender and almost all the liquid has evaporated, about 5 minutes. Stir in lemon zest and remaining rosemary; season to taste with salt and pepper.
Cut steak into thin slices and serve with the vegetables.
Note: based on recipe from South Beach Diet Book Quick & Easy Cookbook.
There are 406 calories in 1 serving of Beef with Asparagus and Mushrooms.