Cut peppers in half lengthwise through stems. Remove and discard seeds and membrane. If desired, set 2 pepper halves with stems aside, and reserve a third half for another use. Remove and discard stems from remaining 3 pepper halves; slice pepper halves into thin strips.
Coat a medium nonstick skillet with cooking spray; place over medium-high heat until hot. Add pepper strips and onion; saute 4 minutes. Add chicken broth and remaining ingredients; saute 2 minutes. If desired, spoon pepper mixture evenly into reserved pepper halves.