Thinly slice onions and pepper into strips. Mince garlic.
Add oil to skillet. Add onions. Cook on medium heat for 2-4 minutes, until fragrant. Add peppers. Sprinkle with ginger and pepper. Stir fry for 5 minutes until crisp-tender. Add soy sauce and vinegar. Add garlic. Cook until liquid is gone and garlic is cooked.