1. Preheat broiler to high.
2. Place baguette cubes on a baking sheet; coat with cooking spray. Broil 2 minutes or until edges are browned, turning once.
3. Reduce oven temperature to 425°.
4. Combine oregano and next 5 ingredients (through crushed red pepper) in a large bowl, stirring with a whisk; set aside.
5. Heat a large ovenproof skillet over medium-high heat; coat pan with cooking spray. Sprinkle chicken evenly with black pepper and salt. Place chicken in pan; cook 4 minutes on each side or until browned. Place pan in oven, and bake at 425° for 10 minutes or until chicken is done. Remove pan from oven. Let chicken stand 5 minutes; slice thinly across the grain.
6. Add bread cubes, lettuce, bell pepper, pepperoncini peppers, and feta to bowl with oregano mixture; toss well. Place about 1 1/3 cups salad on each of 4 plates. Top each serving with about 3 ounces chicken.