Thinly slice beef into bite-size strips. Spray a wok or large skillet with nonstick spray coating. Heat wok or skillet over high heat. Add broccoli, carrot, onion, green pepper; stir-fry for 7 minutes. Add pea pods, mushrooms, and tomatoe; stir-fry for 2 minutes. Remove vegetables. Add cooking oil; heat over high heat. Stir-fry beef in hot oil 3 minutes. Combine quarter cup cold water and soy sauce; blend in cornstarch. Add to wok or skillet. Cook and stir till bubbly. Return vegetables to wok; heat through. Spoon mixture into halved pita bread rounds.