Wash and slice the zucchini and yellow squash into thin rounds.

Slice the bell pepper and onion, and mince the garlic.

Heat olive oil in a wok over medium-high heat.

Add the onion and garlic, sauté for 2 minutes until fragrant.

Add the zucchini, yellow squash, and bell pepper. Stir-fry for about 8-10 minutes until vegetables are tender but still crisp.

Season with salt, black pepper, and soy sauce if using. Stir well to combine.

Remove from heat and serve immediately.