If you're not a fan of mushrooms, there are plenty of other ingredients you can use in a beef wellington. Try swapping out the mushrooms for some chopped up bacon or ham. You could also use a mix of different vegetables, like diced carrots, celery, and onions. If you're looking for a more substantial filling, you could try using cooked rice or quinoa. Just be sure to adjust the cooking time accordingly. Whatever you choose, just make sure the beef is the star of the show.there are a few different options that can be used in place of mushrooms in a beef wellington. One option is to use a different type of mushroom, such as portobello mushrooms. Another option is to use a different type of protein altogether, such as chicken or pork. Finally, you could also use a vegetarian option, such as tofu or tempeh.