Whisk together lime juice, lime zest, minced garlic, minced cilantro, oil, brown sugar, chili powder, cumin (if using), salt, and black pepper in a large bowl to make the marinade.
Add the chicken to the bowl and toss until fully coated in the marinade; let sit for a few minutes while you preheat the cooking surface.
Preheat a grill or skillet to medium-high and lightly grease with oil or nonstick spray.
Cook the chicken 5–8 minutes per side, until cooked through and the internal temperature reaches 165°F (74°C). Discard any excess marinade and transfer chicken to a cutting board to rest 5 minutes, then slice.
While the chicken rests, add the sliced bell peppers to the same hot pan and cook 3–4 minutes, until slightly charred and tender.
Let the chicken and peppers cool to room temperature before assembling.
Divide 1 cup cooked rice among the 4 meal-prep containers, then evenly distribute the sliced chicken and cooked peppers into each container. Seal and refrigerate.
