Drain peaches and save the liquid. Mix cornstarch with the peach liquid and set aside.
Heat oil in frying pan over medium high heat. Add onions and sauté for 2 minutes. Add chicken and stir to combine. Cook for 8 to 10 minutes or until chicken is cooked through, stirring occasionally.
Add peaches to pan and stir to combine. Pour liquid in the pan. Bring to a boil, stirring constantly. Reduce heat to medium low and simmer until liquid has thickened, about 5 minutes. Serve over a bed of rice.