1. In a pot, bring 2 1/2 cups of water to a boil. Add the soaked brown rice and cook until the rice is tender, about 40-45 minutes. Drain any excess water and set the rice aside.
2. In a large pan or wok, heat the oil over medium heat. Add the chopped onion and sauté until it becomes translucent.
3. Add the minced garlic and grated ginger, cooking for 1-2 minutes until fragrant.
4. Add the bell pepper, carrot, broccoli, and peas. Stir-fry the vegetables for 5-7 minutes, or until they are tender but still crisp.
5. Add the cooked brown rice to the pan with the vegetables and stir well to combine.
6. Drizzle soy sauce and rice vinegar or lemon juice over the rice and vegetables. Stir until the rice is evenly coated with the sauce.
7. Season with salt and pepper to taste, and stir-fry for another 2-3 minutes to heat through.
8. Garnish with sesame seeds or spring onions if desired, and serve.

Serving Suggestions: Serve brown rice vegetable stir-fry as a light, healthy meal or pair it with a protein like grilled chicken, tofu, or fish for a complete dish.