This colorful salad is a healthy and tasty side dish.
Cut off ends of oranges; using a paring knife, remove peel, pith, and outer membranes, following the curve of the fruit. Working over a bowl to catch the juices, cut between sections to remove whole segments; add segments to a large bowl. Squeeze juice from membranes into a bowl; measure out 3 tablespoons juice; reserve remaining juice for another use.
In a small bowl, whisk together reserved orange juice, vinegar, and olive oil; season with salt and pepper.
In a large bowl, combine oranges, lettuce, avocado, and radishes. Drizzle with dressing as desired, and toss gently to combine. Serve immediately.
To segment an orange, peel and trim it. Then hold the orange over a bowl and release each segment by cutting toward the center along the membranes -- first on one side of the segment, then on the other.