Rinse the quinoa thoroughly under cold water, then combine with 0.5 cup water in a small saucepan and bring to a boil.
Reduce heat to low, cover, and simmer the quinoa for 15 minutes or until water is absorbed; fluff with a fork and set aside.
Season the chicken breast evenly on both sides with the sea salt, black pepper, and dried oregano.
Heat a non-stick skillet over medium-high heat and cook the chicken for 6-7 minutes per side until the internal temperature reaches 165°F.
While the chicken rests, whisk together the extra virgin olive oil, fresh lemon juice, and minced garlic in a small bowl to create the vinaigrette.
In a large serving bowl, combine the cooked quinoa, baby spinach, diced cucumber, and halved cherry tomatoes.
Slice the chicken into strips and place them over the quinoa base.
Drizzle the lemon-herb vinaigrette over the entire bowl and toss gently to combine before serving.