Light a charcoal grill and let burn to a gray ash (or preheat a gas grill to medium-high). Set grill rack 2 inches from heat source. Grill poblano peppers, covered, turning often, until skins are charred, about 10 minutes. Transfer to a bowl, cover and let stand until cool enough to handle. Peel, cut off tops, discard seeds and coarsely chop flesh.
Combine peppers, black beans, fresh corn, red bell pepper, chili powder, lime juice and olive oil in a bowl. Stir in cilantro; season with salt and pepper.