In a medium bowl, combine tenderloin, dried oregano, soy sauce and Jalapeño. Let everything marinate for 20 minutes.
Heat oil in the large non-stick pan and on the medium heat. Add minced onion and cook until translucent, about 5-7 minutes.
Add tenderloin and Jalapeño mixture and continue cooking for 10 minutes.
Add carrots and cook for another 5 minutes.
Add potato, chicken stock, cover the lid and cook for 10 -15 min minutes, stirring occasionally until potato is cooked through.
Add salt and pepper to a taste.
Add butter, red, yellow and green bell peppers, garlic and cook for 5-10 minutes, until peppers are soft stirring the stew from time to time.