Preheat the oven to 350°F. Spray a rimmed baking sheet with nonstick spray. Add the olive oil and diced onion to a large skillet and fry over medium-high heat, stirring frequently for about 5 minutes until the onion is softened and translucent.
Cut the whole block of slider rolls in half, top and bottom, and place the bottom halves into the baking dish. Evenly spread all of the ground beef over the bottom half of the rolls. Then sprinkle the grated cheese over the beef and add the top halves of the buns.