In a medium skillet, heat the olive oil over medium-high heat. Add the ground beef and taco seasoning, breaking the meat apart as it cooks. Continue cooking until browned and cooked through, approximately 5-7 minutes. Drain excess fat if needed.

Lay out one flour tortilla on a clean surface. Spread about 1/2 cup of cooked beef evenly across half the tortilla. Top with 1/2 cup shredded cheddar cheese, and any additional toppings like diced tomatoes or shredded lettuce. Fold the tortilla in half, covering the filling.

In the same skillet, reduce to medium heat. Carefully place the folded quesadilla onto the skillet and cook for 2-3 minutes on each side, or until the cheese is melted and the tortilla is golden brown. Repeat with remaining tortillas.

Once cooked, remove quesadillas from the skillet and let them sit for a moment before slicing them into wedges. Serve hot with guacamole, sour cream, or salsa for dipping.