Heat a large skillet over medium-high heat and add the olive oil.
When the oil is hot, add the chicken pieces and half of the taco seasoning; cook undisturbed for 2 minutes, then flip and cook another 2–3 minutes, stirring occasionally, until the chicken reaches 165°F and is cooked through. Remove the chicken from the skillet and set aside.
Add the drained corn to the hot skillet in a thin single layer; let cook without stirring for 3–4 minutes, then stir and cook an additional 2–3 minutes until the corn has golden-brown charred spots. Remove and set aside with the chicken.
Reduce the heat to low and pour in the Alfredo sauce, undrained diced tomatoes with green chiles, milk, and the remaining taco seasoning; stir to combine and bring the mixture to a gentle simmer.
Add the tortellini to the sauce, stir to coat, cover the skillet, and simmer for about 5–7 minutes or until the tortellini are tender.
Return the cooked chicken and charred corn to the skillet, stir to combine and heat through.
Garnish with chopped cilantro and serve.