Heat the oil in a wide skillet or steep-sided stir-fry pan. Add the garlic and sauté over low heat until golden.
Add the wine, bell peppers, squash, asparagus, and optional scallions.
Sauté over medium-high heat, stirring frequently, until all the vegetables are tender-crisp to your liking, 5 to 8 minutes. Season with salt and pepper, and serve.