In a mixing bowl, combine olive oil, red wine vinegar, minced garlic, oregano, salt, and pepper. Add the flank steak and coat well. Marinate for at least 15 minutes.

Preheat the grill to medium-high heat. Grill the marinated steak for about 4-5 minutes on each side for medium-rare, or until desired doneness. Let it rest for 5 minutes before slicing.

While the steak is resting, prepare the vegetables. In a large bowl, combine cherry tomatoes, cucumber, red bell pepper, red onion, feta cheese, and olives.

In a small bowl, whisk together olive oil, lemon juice, dijon mustard, honey, salt, and pepper until well combined.

In serving bowls, layer cooked quinoa, sliced steak, and the vegetable mixture. Drizzle with dressing and serve immediately.