Combine quinoa and water in a medium saucepan. Bring to a boil, then reduce heat to low, cover, and simmer for 15 minutes or until water is absorbed. Fluff with a fork and set aside.
Season steak strips with olive oil, oregano, garlic powder, salt, and pepper.
Heat a large skillet or grill pan over medium-high heat. Sear the steak strips for 3 to 4 minutes per side until desired doneness (approx. 135°F/57°C for medium-rare).
Assemble bowls by dividing the cooked quinoa evenly among four serving bowls.
Layer the baby spinach, tomatoes, cucumber, red onion, and olives over the quinoa base.
Top each bowl with the seared steak strips.
Garnish with crumbled feta cheese and fresh chopped parsley.
Serve with a dollop of tzatziki sauce and a lemon wedge on the side.