Rinse the quinoa under cold water to remove any bitterness. In a medium saucepan, combine the quinoa and water (or beef broth). Bring to a boil, then reduce heat to low and cover. Simmer for about 15 minutes, or until the quinoa is cooked and fluffy. Set aside.
While the quinoa is cooking, heat the olive oil in a large skillet over medium heat. Add the diced onion and garlic, sautéing until soft and translucent, about 3-4 minutes.
Add the ground beef to the skillet, breaking it apart with a spoon. Cook until browned, about 5-7 minutes, ensuring it is fully cooked. Drain any excess fat if necessary.
Stir in the diced bell pepper and zucchini, cooking until they are slightly tender, about 5 minutes.
Season the mixture with cumin, paprika, salt, and pepper. Stir to combine and cook for an additional 2-3 minutes.
Fluff the cooked quinoa with a fork and then mix it into the beef and vegetable mixture. Combine well to incorporate all the flavors.
Serve the quinoa bowl in individual dishes, garnishing with fresh parsley if desired.