Remove stems from chard and slice them into 3/8-inch pieces.

Chop the chard leaves.

Heat vegetable oil in a large pot over medium-high heat.

Add chard stems, chopped onion, and diced carrots to the pot.

Cook, stirring frequently, until softened (about 5-7 minutes).

Add minced garlic, minced seeded chipotle chiles, and dried oregano to the pot.

Cook and stir for 20-30 seconds, or until fragrant.

Add reduced-sodium chicken broth, boneless skinless chicken breast half, and long-grain rice (or quinoa) to the pot.

Bring the mixture to a boil.

Turn the chicken breast.

Reduce heat to low, cover the pot, and simmer for 20-25 minutes, or until the chicken is no longer pink and the rice is tender.

Remove the chicken from the pot and let it cool slightly.

Add chopped chard leaves to the pot.

Increase heat to medium and cook, uncovered, for 3-4 minutes, or until the chard is tender.

Shred the cooled chicken into bite-sized pieces.

Return the shredded chicken to the soup.

Garnish each serving with cubed avocado and a lime wedge.