Gently mix together prepared meatballs with marinara sauce. Set aside.
Place opened buns onto a large cookie sheet.
Mix together olive oil with garlic and oregano and brush on the opened sides of the buns.
Toast buns for 5 minutes, or until just browned.
Remove buns from the oven and place 2 slices of provolone cheese on each bun, slightly overlapping to cover the surface of the bun. Top with 3 large (or 4 smaller) meatballs and an additional slice of cheese.
Return to oven and bake for 5-7 minutes or until cheese is melted.