Season chicken breasts on both sides with salt, pepper, oregano, and garlic powder.
Heat olive oil in a large skillet over medium heat. Cook chicken for 5–6 minutes per side until golden and cooked through. Set aside.
In the same skillet, sauté minced garlic for 30 seconds until fragrant.
Pour in white wine or chicken broth and scrape up browned bits from the skillet.
Add halved tomatoes, olives, and capers. Stir and cook for 5–7 minutes until tomatoes soften.
Return chicken to skillet, spoon sauce over top, and simmer for 3–5 minutes.
Transfer mixture to pressure cooker. Seal and cook for 8 minutes with natural release. Finish by stirring in spinach and topping with feta before serving.
Notes
Leftovers can be refrigerated for up to 3 days or frozen for up to 3 months. To reheat, gently warm in a skillet or microwave.