In a small bowl or measuring cup, whisk together ingredients for the sauce.
In a large skillet, heat oil over medium high heat until hot then add the bell peppers. Cook until softened, about 5-7 minutes. Add the chicken and cook through, about 7-10 minutes.
Pour the sauce on top then toss to coat and let simmer. Remove from heat, season with salt and pepper, then stir with a spatula until evenly distributed. Serve over white rice and top with chopped peanuts and green onions, if desired.