Combine rinsed quinoa and chicken broth in a medium saucepan over high heat. Bring to a boil, then reduce heat to low, cover, and simmer for 15 minutes or until liquid is fully absorbed.
Remove quinoa from heat. Stir in lemon juice, lemon zest, and 1 tablespoon of olive oil. Fluff with a fork and set aside.
In a mixing bowl, toss the cubed chicken with dried oregano, garlic powder, salt, pepper, and 1 tablespoon of olive oil until evenly coated.
Heat the remaining 1 tablespoon of olive oil in a large non-stick skillet over medium-high heat. Add the chicken and cook for 8 to 10 minutes, stirring occasionally, until golden brown and the internal temperature reaches 165°F (74°C).
In a separate small bowl, toss together the diced cucumber, cherry tomatoes, and red onion.
Distribute the lemony quinoa equally among four meal prep containers or bowls. Top each with a portion of the cooked chicken, the cucumber-tomato salad, 2 tablespoons of crumbled feta, and a dollop of tzatziki sauce.