To prepare dressing, combine first 6 ingredients, stirring with a whisk until well blended. Cover and chill.
Prepare grill to medium heat.
To prepare salad, cook beans, peas, and carrots in boiling water 3 minutes or until crisp-tender. Drain and plunge into ice water; drain. Place mixture in a large bowl, and add onion slices. Lightly coat vegetable mixture with cooking spray. Sprinkle with 1/2 teaspoon pepper and garlic salt; gently toss to coat.
Place vegetable mixture in a wire grilling basket coated with cooking spray. Place grilling basket on grill rack, and grill 7 minutes on each side or until lightly browned. Arrange 1 1/2 cups of lettuce on each of 4 salad plates. Divide the grilled vegetables and radishes evenly among servings. Serve 1/4 cup dressing with each salad.