Heat the oven to 375ºF. Line a baking sheet with aluminum foil.
Lay a tortilla on a work surface and spread with a thin layer of beans, leaving a 1 inch border all around. Sprinkle with cheese, onions, peppers. Place chicken in a line across the center of the burrito. Fold one inch of the tortilla over from the bottom, then fold in the sides and continue to roll the burrito up. Place seam side down on the prepared baking sheet and continue with the remaining tortillas.
Place in the oven and bake until hot, crispy, and slightly browned, about 10 minutes. If desired, serve with salsa and sour cream.