Heat a large skillet or sauté pan over medium-high heat and add the olive oil.
Add the chopped bell pepper and sauté for 2 minutes.
Add the broccoli florets, stir, and continue to sauté 3–4 minutes until partially softened; remove the vegetables from the skillet and set aside.
Place the whole chicken breasts in the now-empty skillet and add the minced garlic, dried quinoa, 3 1/2 cups chicken broth, 1/2 teaspoon salt, 1/2 teaspoon crushed red pepper, and 1/4 teaspoon black pepper; stir to combine and bring to a simmer.
Once it reaches a simmer, lower the heat to maintain a gentle simmer and cook, uncovered, until the chicken is cooked through, the broth is mostly absorbed, and the quinoa spirals have separated, about 18–20 minutes; add up to 1/2 cup more broth if the pan becomes too dry.
Remove the chicken, chop it into bite-size pieces, and return it to the skillet.
Stir in the sautéed vegetables, pecan pieces, dried cranberries, and chopped scallions; taste and adjust seasoning with additional salt and pepper as needed.
Serve the mixture warm.