Set the Instant Pot to sauté mode, add olive oil, and cook onion and garlic until soft.
Add chicken, season with salt, pepper, and oregano, then brown lightly.
Stir in bell pepper and zucchini, cooking for 2 minutes.
Add rice, broth, and lemon juice. Stir to combine.
Close the lid, set valve to sealing, and cook on high pressure for 10 minutes.
Allow natural release for 5 minutes, then quick release remaining pressure.
Stir in olives and top with feta cheese and parsley before serving.