In a medium bowl, combine the cut chicken thighs, 2 tbsp olive oil, 1 tbsp lemon juice, dried oregano, garlic powder, 1/4 tsp salt, and 1/4 tsp black pepper. Toss to coat evenly. Let marinate for at least 10 minutes while you prep other ingredients, or up to 30 minutes.

Heat 1 tbsp olive oil in a large Dutch oven or deep oven-safe skillet over medium-high heat. Add the chicken in a single layer (you may need to do this in batches to avoid overcrowding). Sear for 3-4 minutes per side until nicely browned, but not cooked through. Remove the chicken from the pot and set aside.

Reduce heat to medium. Add the chopped yellow onion to the pot and sauté for 3-5 minutes until softened and translucent. Add the minced garlic and cook for another minute until fragrant, being careful not to burn it.

Stir in the uncooked orzo pasta, coating it with the residual oil and aromatics. Pour in the chicken broth and add the chopped sun-dried tomatoes. Bring the mixture to a simmer, scraping up any browned bits from the bottom of the pot.

Return the seared chicken pieces to the pot, nestling them into the orzo mixture. Reduce the heat to low, cover the pot, and simmer for 12-15 minutes, or until the orzo is al dente and most of the liquid has been absorbed. Stir occasionally to prevent sticking.

Remove the pot from the heat. Stir in the fresh spinach, crumbled feta cheese (reserving some for garnish), and 1 tbsp fresh lemon juice. Stir until the spinach wilts and the feta is just warmed through. Taste and adjust seasoning with additional salt and pepper if needed.

Serve immediately, garnished with extra crumbled feta and fresh chopped parsley, if desired.