Heat olive oil in pressure cooker over medium-high heat (or using brown setting on an electric pressure cooker.) Sprinkle chicken with salt and pepper. Working in batches cook chicken until golden brown, about 5 minutes total, adding more oil as necessary. Transfer chicken to plate.
Add onion to the pressure cooker; sauté until onion is soft, scrapping up browned bits, about 4 minutes. Add garlic, oregano and red pepper flakes and cook until fragrant, about 1 minute. Add bay leaf, tomatoes and chicken broth; return chicken to pressure cooker and press into tomatoes until they are mostly covered.
Place lid on pressure cooker and lock in place. Cook on high pressure for 10 minutes. Release pressure using quick release valve and remove lid. Add green peppers and stir into mixture. Lock lid in place again, bring to high pressure and cook for 2 more minutes. Use quick release and remove lid. Remove bay leaf. Season to taste with salt and pepper. (If a thicker sauce is desired, you can remove the chicken to a plate and simmer sauce until it is the desired thickness. Do this before seasoning to taste with salt and pepper.)
Serve over rice or pasta