Bring a large pot of lightly salted water to a boil. Cook linguine at a boil until tender yet firm to the bite, about 11 minutes. Drain.
Combine minced onion, seafood seasoning, oregano, basil, garlic powder, red pepper flakes, salt, and pepper in a bowl.
Heat olive oil in a saucepan over medium-high heat. Add onion mixture; cook, stirring constantly, until fragrant, about 1 minute. Stir in mushrooms to coat with onion mixture. Add clams with juice. Bring to a simmer; reduce heat and simmer until flavors combine, about 5 minutes.
Toss clam sauce with pasta in a large bowl. Top with dried parsley.