Preheat a grill to medium high. Combine 2 tablespoons olive oil, the garlic, 1 teaspoon each cumin and oregano and the lime juice in a small baking dish. Add the steak, turn to coat and season well with salt and pepper; set aside at least 10 minutes.
Meanwhile, combine the black beans with their liquid, the rice, 1 cup water, the remaining 1/2 teaspoon each cumin and oregano, 1/2 teaspoon salt and a few grinds of pepper in a medium saucepan. Bring to a boil over high heat, stirring occasionally to prevent sticking. Reduce the heat to low, cover and cook until the liquid is absorbed and the rice is tender, about 17 minutes. Remove from the heat and set aside.
Combine the bell peppers, onion, remaining 2 tablespoons olive oil and a big pinch each of salt and pepper in a large bowl. Grill the peppers and onion, turning occasionally, until browned in spots and crisp-tender, 4 to 5 minutes. Return to the bowl, add the olives and toss. Grill the steaks until browned, about 3 minutes per side for medium rare; transfer to a cutting board.
Fluff the rice and divide among plates. Slice the steak and serve with the rice, vegetables and lime wedges.