Vinaigrette: Whisk all the ingredients together, except oil, until smooth. Slowly drizzle in the olive oil and whisk until combined. Season with salt and pepper to taste.;
Seafood: Brush the tuna, shrimp and scallops with the olive oil and season with salt and pepper to taste. Grill the tuna to rare, grill the shrimp and sea scallops until just cooked through, about 2 to 3 minutes per side.;
Vegetables: Preheat grill. Brush peppers and squash with oil and season with salt and pepper to taste. Grill each for 5 to 6 minutes on each side, until just cooked through.
Place the green beans and tomatoes in bowls. Toss each with 2 tablespoons of the vinaigrette and season with salt and pepper to taste.
Line 8 plates with the red leaf lettuce. On each plate arrange 2 scallops, 3 shrimp and 1 piece of the tuna. Divide the squash, beans, roasted pepper, tomatoes and olives among the plates. Drizzle the remaining dressing over the salad.