Heat the oven. Heat the oven to 425°F convection or 450°F conventional. Put racks in the upper and lower thirds. Lightly oil two rimmed half-sheet pans or line them with foil and lightly oil the foil.

Start the rice. Cook the rice according to its package directions while the fajita mixture roasts.

Prep. Cut the chicken into thin bite-size strips, the bell peppers into strips, and the red onion into thin wedges.

Season. Put the chicken, peppers, and onion in a large bowl. Add the fajita seasoning and neutral oil, then toss very thoroughly until evenly coated. Reserve the lime juice for after roasting so the food browns more readily.

Spread across two pans. Divide the mixture evenly between the two sheet pans and spread it into shallow, uncrowded layers. Avoid piling the pieces on top of one another; crowding traps moisture and steams the food.

Roast. Roast for 10 minutes. Toss the contents of each pan, then swap the pans between racks and rotate them front to back. Roast for another 8–12 minutes, until the vegetables have browned edges and the thickest chicken pieces reach 165°F / 74°C.

Optional extra char. For darker edges, broil one pan at a time for 2–3 minutes, watching constantly. Do not put parchment paper under the broiler.

Finish and portion. Drizzle the roasted chicken and vegetables with the lime juice and toss. Divide the rice among 4 meal-prep containers or bowls, top with the fajita mixture, and cool before covering if storing. Refrigerate promptly.