Combine first 6 ingredients. Shape mixture into 12 (4-inch) patties. Fold cheese slices into quarters; place cheese on each of 6 patties. Top with remaining 6 patties, pressing to seal edges.
Grill, covered with grill lid, over medium-high heat (350° to 400°) 4 to 5 minutes on each side or until done. Serve on rolls with Tex-Mex Secret Sauce and desired toppings.
Note: For testing purposes only, we used McCormick Fajita Seasoning and Sargento Monterey Jack Cheese With Peppers.