Combine first 6 ingredients in a bowl; stir well, and set aside. Coat a nonstick skillet with cooking spray; place over medium heat until hot. Add mushrooms and green onions; saute 2 minutes. Increase heat to medium-high, and add egg mixture; cook 2 minutes. Cover and cook an additional minute or until center is set. Remove from heat; top with cheese. Loosen omelet with a spatula; fold in half. Yield: 4 servings (serving size: 1 pita half). Per serving: 239 Calories; 8g Fat (28% calories from fat); 15g Protein; 30g Carbohydrate; 103mg Cholesterol; 407mg Sodium NOTES : To serve, slide omelet onto serving plate; cut into four portions. Line each pita half with 2 tomato slices; place one omelet portion into each half. Recipe by: Cooking Light, Mar/Apr 1993, page 120 Posted to MC-Recipe Digest V1 #410 by igor@digex.net on Jan 28, 1997.