Prepare the grill for direct cooking over high heat (450° to 550°F).
In a large serving bowl combine the dressing ingredients. Set aside.
Bring a large pot of salted water to a boil. Add the macaroni and cook according to package directions until al dente; drain, rinse under cold water and drain again. Transfer the macaroni to the serving bowl with the dressing and toss to combine.
Brush the corn all over with the oil, and then grill over direct high heat, with the lid closed, until browned in spots and tender, 8 to 10 minutes, turning occasionally. Remove from the grill. When cool enough to handle, cut the kernels off the cobs.
Add the corn, bell peppers, tomatoes and scallions to the bowl with the macaroni and mix well.
Refrigerate until ready to serve. Just before serving, gently mix in the basil.