Fill a large pot with water and bring to a boil. Add spinach fettuccine and cook according to package directions. Drain.
Meanwhile, heat a large pan with 1 1/2 Tbsp olive oil to medium high heat. When hot add sliced peppers and onions and saute about 4-5 minutes until they are caramelized. Remove from pan.
Using same pan, add the remaining olive oil and cook sliced chicken until cooked through and you can see no more pink. Return veggies to the pan and add fajita seasoning and the amount of water needed according to package directions.