Large flour tortillas are able to accommodate generous fillings, which may be why they're so popular in Northern Mexico and the US. These satisfying quesadillas are stuffed with cheese and ground beef flavored with oregano, ancho chili powder and garlic.
Heat the olive oil in a large skillet over medium heat. Add the garlic and chili powder and cook 1 to 2 minutes. Add the beef, oregano, 1 teaspoon salt, and pepper to taste. Cook, breaking up the meat with a spoon, until it is no longer pink, about 2 minutes. Add the scallions and cook 5 to 6 more minutes.
Heat a large griddle or skillet over medium heat. Brush 1 side of each tortilla with olive oil. Place 2 tortillas on the griddle (or 1 if using a skillet), oiled-side down, and scatter about one-quarter of the cheese on each. Cook until the bottoms are golden brown and the cheese is melted. Put about a quarter of the beef mixture on half of each tortilla and fold into a half-moon. Continue to cook until the quesadillas are crisp, turning once. Repeat to make 4 quesadillas.
Cut into wedges and top with salsa and/or sour cream.