1. Preheat oven to 450°.
2. Combine sliced avocado and juice in a small bowl; cover and refrigerate. Trim both ends of corn cobs, leaving husks from corn intact. Place the corn on a baking sheet. Bake at 450° for 20 minutes or until tender. Cool. Remove husks from corn; scrub silks from corn. Cut kernels from ears of corn; discard cobs.
3. Reserve 4 whole lettuce leaves. Chop remaining lettuce to measure 4 cups. Combine chopped lettuce, avocado mixture, corn, and radishes. Spoon lettuce mixture into lettuce leaves. Serve with Avocado-Herb Dressing.