In a bowl, toss the chicken breasts with 1 tablespoon of olive oil and 2 tablespoons of fajita seasoning.
Slice the bell peppers and onion into strips. Place them in a separate bowl and toss with 1 tablespoon of olive oil and 1 tablespoon of fajita seasoning.
Preheat your grill or grill pan to medium-high heat.
Grill the chicken breasts for 5-7 minutes per side, or until cooked through (165°F/74°C).
Add the sliced peppers and onions to the grill or grill pan. Cook for 5-7 minutes, stirring occasionally, until they are tender-crisp and slightly charred.
Remove the chicken from the grill and let it rest for 5 minutes before slicing it into strips.
Divide the cooked rice or quinoa evenly among bowls. Top with the grilled vegetables and sliced chicken.
Garnish with your favorite toppings and a squeeze of lime juice. Serve immediately.