¾ cup olive oil | ¼ cup balsamic vinegar | 1 large red onion, cut into ¾-inch-thick rounds | 12 baby beets, stems trimmed to 1 inch, peeled, halved lengthwise | 3 small zucchini, each cut lengthwise into 4 slices | 1 small eggplant, diced into 1-inch pieces | 2 large red bell peppers, cut into 2-inch-wide strips | 6 slices country-style French bread | Additional olive oil | 10 cups mixed baby greens | 3 tablespoons chopped fresh basil | 2 tablespoons chopped fresh chives or green onions | 1 tablespoon chopped fresh marjoram | ¾ cup chilled fresh mild goat cheese (such as Montrachet), crumbled (about 3 ounces) | ½ cup freshly grated Pecorino Romano cheese (about 2 ounces) | ¾ cup brine-cured black olives (such as kalamata)
Heat grill on medium-high heat. Whisk ¾ cup oil and vinegar in medium bowl until well-blended. Place onion, beets, zucchini, eggplants and red bell pepper on baking sheet. Brush both sides with some of the vinaigrette. Sprinkle vegetables with salt and pepper. Grill vegetables until just cooked through, about 10 minutes per side for beets, 6 minutes per side for onion and 4 minutes per side for zucchini, eggplant and peppers. Remove the vegetables according to individual cooking requirements. Vegetables can be grilled 1 hour ahead. Let stand at room temperature. Brush bread with additional olive oil; sprinkle with pepper. Grill bread until beginning to brown, about 2 minutes per side.