Position oven racks in upper and lower thirds of oven. Preheat oven to 400°F.
Place onion, bell peppers, and olive oil in a medium bowl and toss to combine. Divide mixture among two large baking sheets; set aside.
Remove pollo asado from package and slice into 2x1-inch strips. Divide pollo asado between baking sheets. Place sheets on upper and lower racks of oven and bake 25-30 minutes, rotating halfway through, until chicken reaches 165°F. Remove from oven and let cool slightly.
While fajitas bake, slice limes into wedges. Rinse and dry cilantro and remove stems. Warm tortillas in a skillet over medium heat, or directly over flame, if desired.
To assemble, fill a warm tortilla with fajitas and top with pico de gallo, cilantro, and a squeeze of lime. Repeat until satisfied.
