Thaw shrimp, if frozen. Peel and devein shrimp. Rinse shrimp; pat dry with paper towels. Place shrimp in a medium bowl. For marinade, in a small bowl stir together 1 tablespoon of the olive oil and the lemon-pepper seasoning. Pour marinade over shrimp in bowl; toss to coat. Cover and marinate in the refrigerator for 1 hour, stirring occasionally.
Lightly brush pita bread and sweet pepper quarters with the remaining 1 tablespoon olive oil.
On a grill pan, grill sweet pepper quarters, cut sides up, over medium high heat about 10 minutes or until pepper skins are blistered and dark. Remove peppers from grill. Wrap peppers in foil and let stand for 20 minutes. Meanwhile, grill shrimp for 6 to 8 minutes or until shrimp turn opaque, turning once halfway through grilling. Grill pita bread for 2 to 4 minutes or until lightly toasted, turning once halfway through grilling.
Remove and discard skins from peppers. Coarsely chop peppers. Cut pita bread into 1-inch pieces. In a large bowl combine grilled peppers, bread, and shrimp. Stir in tomato, cucumber, radish, and green onion. Drizzle with vinaigrette. Toss gently to coat. Season to taste with salt and black pepper. Serve immediately.