Preheat oven to 350°F (180°C). In a skillet set over medium heat, add the oil and the chicken breasts and cook about 8 min. per side, or until they reach an internal temperature of 165°F (74°C). Remove from skillet to a plate; once cool enough to handle, cut into bite-size pieces.
In large bowl, mix together chicken, pasta, soup, spinach and red pepper. Pour mixture into 9 x 13-in. (23 x 32-cm.) baking dish. Sprinkle with cheese.
Bake about 20 min., or until soup is bubbling and cheese begins to brown.