Brush vegetables with olive oil and, if desired, sprinkle each side with freshly ground pepper and salt. Lay vegetables perpendicular to wires on rack of an uncovered grill directly over medium to medium-hot coals. Grill onion, eggplant, and pepper rings for 8 to 10 minutes. Grill asparagus, zucchini, and yellow squash for 5 to 6 minutes or until crisp-tender, turning occasionally.
Arrange vegetables on mixed greens. Drizzle with vinegar and sprinkle with basil. Makes 6 side-dish servings.
To use an indoor grill:
Preheat indoor electric grill. Brush vegetables with olive oil and, if desired, sprinkle with salt and freshly ground black pepper. Place vegetables on the grill rack. (If necessary, cook vegetables in batches.) If using a covered grill, close lid. Grill until vegetables are crisp-tender. (For a covered grill, allow 4 to 5 minutes. For an uncovered grill, allow 8 to 10 minutes for eggplant, sweet peppers, and onion, and 5 to 6 minutes for asparagus, zucchini, and yellow squash, turning occasionally to cook evenly.) Serve as above.