To prepare lentils, rinse and drain lentils. Place water, lentils, and bay leaf in a medium saucepan; bring to a boil. Reduce heat and simmer 20 minutes. Drain; discard bay leaf. Combine lentils, red onion, and next 7 ingredients (through garlic) in a large bowl.
To prepare vegetables, combine asparagus and next 6 ingredients (through oil) in a large bowl; toss well to coat. Grill zucchini, peppers, and eggplant 15 minutes, turning once. Grill asparagus 6 minutes, turning once. Place vegetables in a bowl; drizzle with 2 teaspoons vinegar. Sprinkle with remaining ingredients; toss well to coat. Serve with lentils.