01 - Heat olive oil in a large skillet over medium-high heat. Add the ground beef and chopped onion, cooking while breaking the meat apart until thoroughly browned, about 6 to 7 minutes. Season with salt and pepper.
02 - Drain any excess fat from the skillet. Stir in the ketchup and mustard, mixing until the beef is evenly coated and heated through.
03 - Lay the tortillas flat on a work surface. Place one slice of cheddar cheese in the center of each tortilla, then top with a quarter of the beef mixture, shredded lettuce, diced tomato, and pickle slices.
04 - Drizzle mayonnaise over the filling of each wrap. Fold in the sides of the tortilla, then roll up tightly from the bottom to fully enclose the filling.
05 - Wipe the skillet clean and return to medium heat. Place each wrap seam-side down in the skillet and grill for 1 to 2 minutes per side until golden and crisp.
06 - Slice each wrap in half and serve immediately.