Make salad: Preheat grill to medium. Brush corn with oil; season with salt and pepper. Grill for 10 minutes. Cool; cut off kernels. Place in a large serving bowl.
Brush zucchini, eggplant, onion and pepper with oil; season with salt and pepper. Push a metal skewer through onion rings horizontally. Grill vegetables, turning often, until softened but firm, about 7 minutes. Cool; cut into chunks and add to bowl.
Cook lima beans according to package directions; plunge into cold water to stop cooking. Add to bowl with vegetables.
Make vinaigrette: Whisk together all ingredients except oil. Pour in oil in a steady stream, whisking constantly. Pour over veggies; toss. Serve at room temperature.