Preheat oven to 400 degrees.

In a bowl, combine ground beef, bread crumbs, diced onion, garlic salt, and pepper.

Press meat mixture evenly into a 9 x 13 inch baking dish. Bake at 400 degrees for 30 minutes. The meat will shrink as it cooks and pull away from the edges. Carefully drain off grease after cooked.

Top meat with cheese slices and return to the oven for about 2 minutes until cheese is melted.

Remove from the oven and let rest for a minute. Then cut into 20 patties (4 x 5 rows).

Serve on buns with a pickle slice along with mayo, mustard and ketchup. (I placed mayo on the bottom bun and a little squirt of may on mustard on the top bun) Makes 20 sliders.