You can substitute rice, quinoa, or even potatoes for the pasta in this recipe. If you use rice, you will need to cook 4 cups of rice according to the package directions and stir it into the beef mixture before baking. If you use quinoa, you will need to cook 2 cups of quinoa according to the package directions and stir it into the beef mixture before baking. If you use potatoes, you will need to cube 4 potatoes and cook them in a pot of boiling water until they are tender. Drain the potatoes and stir them into the beef mixture before baking.