Scrape the kernels from the corn cobs. In a large skillet, heat 1 tablespoon olive oil over high heat and add the corn. Cook, stirring occasionally, until lightly charred, about 4 minutes. Transfer to a large bowl to cool slightly, then stir in the orzo, tomatoes, onion and basil.
In a small bowl, whisk together the remaining 7 tablespoons olive oil and the vinegar; add the salt, black pepper and cayenne. Pour over the corn salad and toss.