In a wok or big skillet, heat oil over medium heat. Saute garlic until softened. Pour the cornstarch mixture into the wok and add the oyster sauce and ground pepper and bring to a boil. Doing this from the beginning keeps the veggies crisp and helps prevents over-cooking them.

Add the first batch of vegetables: broccoli, cauliflower, carrots and snap peas and cook covered for about 2-3 minutes. Add the rest of the vegetables and cook for another 2-3 minutes or until vegetables are tender-crisp and the sauce has thickened. Season with salt if still needed. Serve hot.