Heat 1 tablespoon of the oil in a large skillet over medium-high heat. Add the sliced bell peppers and onion, season with salt, and cook for about 5 minutes until soft. Transfer to a plate.

Add another tablespoon of oil to the same skillet and heat over medium-high. Add the chicken strips and season with chili powder, cumin, oregano, and about 1/2 teaspoon salt. Cook, stirring occasionally, until golden and cooked through, about 8 minutes. Transfer to a plate and wipe out the skillet.

Add 1 tablespoon of oil to the skillet. Place one tortilla in the pan and sprinkle cheese over half of it. Add one-quarter of the chicken, one-quarter of the pepper and onion mixture, a few avocado slices, and a sprinkle of scallions. Fold the tortilla over.

Cook until golden, about 3 minutes per side, flipping once.

Repeat with the remaining oil, tortillas, chicken, vegetables, avocado, and scallions to make all four quesadillas.

Slice into wedges and serve with sour cream.