Preheat a grill to high. Once heated, brush grates lightly with oil. Season the steak with salt and pepper to taste. Grill the steak until slightly charred and crisp and a thermometer inserted horizontally into the meat registers 130 degrees for medium-rare, 7-8 minutes per side. Set on a cutting board to rest for 10 minutes before slicing.
Whisk the olive oil, 1/2 teaspoon salt and vinegar together in a bowl. Toss with pepper and onion; gently fold in the avocado and cilantro.
Slice the steak against the grain, divide among plates over romaine, top with the pepper and avocado. Serve with Bush's® Black Bean Fiesta Grillin' Beans®.