Wash your hands well with soap and warm water for at least 20 seconds.
Wash squash and zucchini. Trim ends and cut in half lengthwise. Then cut each piece into half-moon pieces about ½ inch thick.
Peel onion and cut into thin strips.
Heat oil in a large skillet over medium-high heat. Add squash, zucchini, onion, garlic powder, pepper and salt to hot skillet. stir to coat vegetables with seasonings.
Cook for 2 to 3 minutes without stirring so the vegetables begin to brown. Stir occasionally while cooking for an additional 5 to 7 minutes.