Preheat the oven to 350 degrees F (175 degrees C). Line two baking sheets with aluminum foil and lightly grease.

Mix together ground beef, bread crumbs, cream of mushroom soup, eggs, Parmesan cheese, and onion soup mix. Shape beef mixture into 2-inch diameter balls; arrange on the prepared baking sheets.

Bake in the preheated oven until no longer pink in the center, about 30 minutes. An instant-read thermometer inserted into the center should read at least 160 degrees F (70 degrees C).