Preheat oven to 500°.
Arrange eggplant in a single layer on a baking sheet coated with cooking spray; lightly coat both sides of eggplant with cooking spray. Bake at 500° for 15 minutes, turning after 8 minutes.
Heat oil in a small skillet over medium-high heat. Add walnuts, oregano, and garlic; sauté 2 minutes. Drop walnut mixture through food chute with food processor on, and process until minced. Drop parsley through food chute with food processor on, and process until minced. Add eggplant, lemon rind, lemon juice, salt, and red pepper, and process until smooth. Spoon eggplant mixture into a bowl, and sprinkle with parsley, if desired. Serve with pita wedges.