Rinse the quinoa under cold water, then combine it with the water in a small pot and bring to a boil.
Reduce the heat to low, cover the pot, and simmer for 15 minutes until the water is absorbed and the quinoa is fluffy.
While the quinoa cooks, slice the chicken breast into bite-sized strips and season them with sea salt, black pepper, garlic powder, and dried oregano.
Heat the olive oil in a large skillet over medium-high heat.
Add the seasoned chicken to the skillet and sear for 5-7 minutes, turning occasionally, until golden brown and cooked through.
Add the sliced bell peppers and red onion to the skillet with the chicken and sauté for 3-4 minutes until the vegetables are tender-crisp.
Stir in the baby spinach and cook for 1 minute just until the leaves are wilted.
Transfer the cooked quinoa to a large bowl and top with the chicken and vegetable mixture.
Garnish the bowl with sliced avocado and crumbled feta cheese, then finish with a fresh squeeze of lemon juice.