Combine quinoa and 1 cup water in a saucepan; bring to a boil, then reduce heat and simmer covered for 15 minutes.
Season chicken with a portion of salt, pepper, and oregano.
Heat olive oil in a skillet over medium-high heat and cook chicken for 6 to 7 minutes per side until internal temperature reaches 165 degrees Fahrenheit.
Rest chicken for 5 minutes before slicing into 0.5-inch strips.
Prepare vinaigrette by whisking extra virgin olive oil, lemon juice, and remaining seasonings in a small vessel.
Divide greens and cooked quinoa into two bowls.
Top with tomatoes, cucumber, onion, avocado, and sliced chicken.
Drizzle vinaigrette over both bowls and serve immediately.