Heat olive oil in a skillet over medium heat. Add the chopped red bell pepper, red onion, and frozen corn. Cook, stirring often, until the vegetables are softened and the onion is slightly translucent, about 6 to 8 minutes. Remove from heat and set aside.

Place the shredded chicken in a medium bowl. Sprinkle on the chili powder, cumin, garlic powder, dried oregano, and salt. Stir until evenly coated. Add the cooked vegetables and stir to combine into the filling.

Assemble the quesadillas. Place a little shredded cheese on the bottom half of each tortilla, add the chicken and veggie filling, then top with more cheese before folding the tortilla over. The cheese on top and bottom holds the quesadilla together when cooking.

Heat a grill pan or large skillet over medium heat. Cook two quesadillas at a time, about 2 to 4 minutes per side, until the tortillas are golden brown and the cheese is fully melted. Lower the heat if the outside browns too quickly before the cheese melts. Slice and serve immediately with guacamole, salsa, and sour cream.