Slice the chicken breast in 1/4 inch strips. Season with the garlic powder, salt, and pepper.
Heat the olive oil in a medium skillet over medium heat. Add the chicken and cook thoroughly, stirring occasionally for about 7-8 minutes.
Once cooked, set aside on a plate.
Cut off the first inch of the tip of the Romaine lettuce and remove the outer 2 or 3 leaves. Quarter the head of lettuce by slicing it from the root end to the tip, then turn it 1/4 turn and slice it again. Now chop the lettuce in 1/2 inch pieces. Be sure to mix the lettuce so the darker top pieces and the lighter bottom pieces are mixed.
Place even amounts of lettuce on 4 plates. Add some bell peppers, cucumbers, tomatoes, olives, red onions, and feta cheese on each plate. Top each plate with some of the cooked chicken.
In a mixing bowl, mix the balsamic vinegar, oregano, parsley, basil, garlic powder, salt, and pepper with a whisk. Slowly drizzle in the olive oil in a thin stream while gently whisking the entire time until all the olive oil has been added to the bowl.
Drizzle some of the balsamic vinaigrette over the salad and chicken.