Heat a large cast-iron skillet over high heat. Char the ears of corn, rotating on all sides, in the dry skillet until lightly blackened and charred, about 15 minutes. Let cool, and then remove the kernels from the cob with a sharp knife.
In a small bowl, whisk together the olive oil, lime juice and salt and pepper to taste.
Add the black beans, tomatoes, rice, red onions, green onions, garlic and cooled corn to a large bowl. Toss with the lime vinaigrette.