Preheat oven to 425 degrees F. Coat a 1 1/2-quart au gratin dish with cooking spray; set aside. Cook pasta according to package directions. Drain and set aside.
Line a 15x10x1-inch baking pan with foil. Lightly coat both sides of each eggplant slice with cooking spray. Place coated eggplant slices in the prepared baking pan. Add sweet pepper quarters to pan with eggplant slices. Roast, uncovered, for 15 to 20 minutes or until eggplant begins to brown and peppers are just tender. Remove from oven; let cool. Cut eggplant and pepper pieces into 3/4-inch cubes. Reduce oven temperature to 350 degrees F.
For lemon dressing, in a small bowl whisk together olive oil, 1 teaspoon of the lemon peel, the lemon juice, and garlic. Whisk in 3 tablespoons of the oregano, the salt, and black pepper; set aside. In another small bowl stir together panko, the remaining 1 tablespoon oregano, and the remaining 1/2 teaspoon lemon peel; set aside.
In a large bowl combine cooked orzo, eggplant, sweet pepper, tuna, artichoke hearts, olives, and feta cheese. Stir in the lemon dressing. Spoon mixture into the prepared baking dish. Cover with foil. Bake for 35 to 40 minutes or until heated through. Sprinkle panko mixture over top. Bake, uncovered, for 5 to 8 minutes more or until panko mixture is golden brown. If desired, serve with lemon wedges.