2 (10-inch) sub rolls, halved horizontally and center hollowed out
1 lb red bell peppers, tender-roasted (procedure precedes) and cut lengthwise into 1-inch strips
2 cups watercress (tough stems discarded)
Special equipment: a well-seasoned cast-iron ridged grill pan
Directions
Rub chicken with 1 tablespoon oil, oregano, 1/4 teaspoon salt, and 1/8 teaspoon pepper and marinate at room temperature 30 minutes.
Whisk together vinegar, garlic, 3/4 teaspoon salt, and 1/8 teaspoon pepper and add 1/4 cup oil in a slow stream, whisking until emulsified. Drizzle cut sides of bread with half of dressing and toss roasted peppers with remainder.
Heat grill pan over moderately high heat until hot, then grill chicken, turning over once, until just cooked through, 4 to 6 minutes total. Make sandwiches with chicken, peppers, and watercress.
