Large shrimp (usually 16 to 20 per pound) are best for this recipe. Smaller ones are harder to grill and get lost in the salad.
Preheat grill to high (450°F to 550°F). Whisk together honey and 2 tablespoons of the olive oil in a medium bowl. Add shrimp; toss to coat.
Generously oil grill grate with grapeseed oil. Grill shrimp, covered with grill lid, until done, about 1 1/2 minutes per side.
Toss together arugula, tomatoes, olives and onion in a large bowl. Add vinegar and remaining 1 tablespoon olive oil and toss. Add shrimp, salt and pepper; toss. Transfer mixture to a platter and sprinkle with oregano. Serve immediately.