Preheat broiler. In the bottom of a broiler pan combine cauliflower, sweet peppers, beans, and onions. In a small bowl combine oil, salt, black pepper, and garlic; drizzle over vegetables, tossing to coat.
Broil 5 to 6 inches from heat for 20 to 25 minutes or just until vegetables are tender and browned, stirring every 5 minutes. Watch carefully the last 5 to 10 minutes of broiling and stir more frequently, if needed, to prevent burning. Remove pan from oven. Sprinkle vegetables with lemon peel and juice; toss gently to coat. Makes 6 to 8 servings.