Heat a grill to high heat.
Lay the steak slices on the grill and sprinkle with salt and black pepper. Grill to medium-rare, 4 minutes per side, or longer if desired. Remove and tent with foil while you prepare the vegetables.
Place a grill pan over high heat and spray with canola oil. Add the onions and bell peppers, season with salt and black pepper and grill until well-marked and have softened, about 10 minutes. Reduce the heat and push the vegetables to the middle of the grill pan, then top with the provolone cheese and let melt.
Arrange the lettuce cups on a platter. Divide the peppers and onions among the lettuce cups and top with the steak slices.