Cook the lo mein noodles according to package instructions; drain and set aside.
Heat vegetable oil in a large skillet or wok over medium-high heat.
Add minced garlic and sauté for about 30 seconds until fragrant.
Toss in sliced bell peppers and stir-fry for 2-3 minutes.
Add broccoli florets and snap peas, cooking for another 3-4 minutes.
Push the vegetables to one side of the skillet.
Add the cooked lo mein noodles to the skillet.
Pour in soy sauce, oyster sauce, and sesame oil, mixing everything well.
Stir-fry for another 2-3 minutes until heated through.
Garnish with chopped green onions before serving.