Wash and prepare all vegetables by slicing and chopping them into uniform pieces.
Heat a large skillet or grill pan over medium-high heat.
Add sesame oil to the pan and let it heat up.
Add minced garlic to the oil and sauté for about 30 seconds until fragrant.
Begin by adding the onions and sauté for 2-3 minutes until translucent.
Add broccoli florets and cook for an additional 2 minutes.
Toss in the carrots and bell peppers, cooking for another 3-4 minutes.
Finally, add zucchini and yellow squash, cooking until tender but crisp.
Pour soy sauce over the vegetables and toss to combine, cooking for another minute.
Season with salt and pepper to taste before serving.