Prepare Ingredients: Make sure all your ingredients are prepped and ready to go before you start cooking.
Heat Oil: In a large skillet or wok, heat the vegetable oil over medium-high heat.
Cook Onion and Garlic: Add the chopped onion and garlic to the skillet, sautéing until fragrant and translucent.
Add Rice: Add the cooked brown rice to the skillet, breaking up any clumps with a spatula. Stir everything together. Stir fry for 2-3 minutes to get some crispy bits.
Season: Pour the soy sauce and oyster sauce (if using) over the rice mixture. Stir well to ensure everything is evenly coated. Season with salt and pepper to taste.
Add Vegetables: Stir in the mixed vegetables and cook until they are tender.
Scramble Eggs: Push the vegetables to one side of the skillet and pour the beaten eggs into the other side. Scramble the eggs until fully cooked, then mix them with the vegetables.
Finish: Garnish with sliced green onions and give the fried rice one final stir. Serve hot.