In a medium saucepan, combine the rinsed quinoa and water. Bring to a boil over medium-high heat.
Reduce heat to low, cover, and simmer for 15 minutes or until quinoa is tender and water is absorbed.
Remove from heat and let quinoa sit covered for 5 minutes. Fluff with a fork and set aside.
Heat the vegetable oil in a large skillet or wok over medium-high heat.
Add the ground beef and cook, breaking it apart with a spatula, until browned and cooked through, about 5 minutes.
Add the diced onion and minced garlic to the skillet and cook for 2 minutes until softened and fragrant.
Add the broccoli florets and cook for 3-4 minutes until tender-crisp.
Push the beef and vegetables to one side of the skillet. Pour the beaten eggs into the empty side and scramble until fully cooked.
Add the cooked quinoa to the skillet and stir to combine all ingredients evenly.
Pour in the soy sauce, oyster sauce, and sesame oil. Stir well to coat the quinoa and beef mixture.
Season with ground black pepper and cook for another 2 minutes, stirring frequently.
Remove from heat and garnish with sliced green onions before serving.