Bring water and quinoa to a boil in a saucepan. Reduce heat to medium-low, cover, and simmer, stirring occasionally, until quinoa is tender and water has been absorbed, about 15 minutes. Remove from heat and let stand for 5 minutes; fluff with a fork and cool to room temperature.

Heat a skillet over medium-high heat; cook and stir pine nuts in the hot skillet until fragrant and toasted, about 5 minutes.

Mix quinoa, spinach, kidney beans, tomatoes, olives, feta cheese, and onion together in a bowl.

Whisk olive oil, vinegar, lemon juice, oregano, salt, and pepper together in a bowl until dressing is smooth; drizzle over quinoa mixture and toss to coat.