Light the grill or heat the broiler. Toss the scallops with the 1 tablespoon oil, 1/4 teaspoon of the salt, and 1/4 teaspoon of the pepper.
In a glass or stainless-steel bowl, whisk together the vinegar and the remaining 1/2 teaspoon salt and 1/4 teaspoon pepper. Add the 1/2 cup oil slowly, whisking.
Grill or broil the scallops, turning once, until they just become opaque in the center, 2 to 3 minutes per side.
In a large glass or stainless-steel bowl, combine the mixed greens, basil, parsley, mint, and chives. Toss the salad with the dressing and put it on plates. Top the salad with the grilled scallops and the capers.
Variations: Substitute grilled shrimp for the scallops. *Flaked cooked salmon would also be delicious in place of the scallops.