Preheat the grill to high heat (450° to 550°).
Vinaigrette: Whisk together all ingredients in a small bowl until emulsified. Set aside.
Steak: Brush the steaks on both sides with the oil and season both sides with salt and pepper.
Cook on a hot grill for 2 to 3 minutes or until the desired internal temperature is achieved.
Rest the steak on a cutting board for 2 minutes before slicing.
To Plate: Serve the spring mix in a large bowl and top off with bell peppers, zucchini, black beans, onion, tomatoes, avocado and sliced steak, and serve alongside vinaigrette.