In a medium bowl, mix the olive oil, garlic salt, parsley, chives, pepper, Old Bay Seasoning, and seasoning salt. Rub the chicken breasts with 1/2 the mixture, and place the breasts in a medium baking dish.
Toss the green bell peppers, tomatoes, and red onion with the remaining olive oil mixture. Arrange over the chicken.
Bake 1 hour in the preheated oven, stirring the vegetables once, until the vegetables are tender, the chicken is no longer pink, and its juices run clear.