Prep the ingredients before you start cooking - cut the veggies into bite-size pieces.
In a medium bowl, combine all sauce ingredients and whisk until smooth.
Cut the chicken breasts into 1-inch pieces, season with garlic powder and pepper, and toss with cornstarch.
Heat two tablespoons of olive oil in a skillet, add chicken, and cook until browned and cooked through.
If needed, add a small splash of oil and sauté onions until softened.
Add broccoli florets and red bell pepper slices, cooking until tender-crisp.
Return the cooked chicken to the skillet, add the sauce, and stir until thickened.
