Bring stock, quinoa, green beans, 1/2 teaspoon salt, oregano, garlic, and red pepper flakes to a boil. Reduce heat to a simmer and cover. Cook for 15 minutes, or until quinoa has absorbed liquid. Allow quinoa to cool slightly for about 5 minutes, if desired.
Place spinach in large bowl and toss with cooked quinoa, mixing together allowing spinach to wilt slightly.
Add in cucumbers and peppers and toss.
In small bowl, combine the juice and zest of a lemon with 1 teaspoon salt, pepper, capers, and olive oil. Pour over quinoa and toss together.
Eat immediately or chill for later consumption.