Preheat medium skillet over medium-high heat; add oil. Add carrot pieces and stir-fry for 2 minutes. (Add more oil as necessary during cooking.) Add zucchini; stir-fry for 1-1/2 to 2 minutes. Add red pepper, mushrooms, and green onion to the skillet; stir-fry about 1 minute or until vegetables are crisp-tender.
Add oyster sauce or soy sauce and garlic powder to the skillet. Stir the vegetables until coated with sauce. Serve immediately. Makes 1 serving.