Bring a large pot of salted water to a boil. Add the spaghetti and cook according to the package directions for al dente. Reserve 1/2 cup of the cooking water for later, then drain the pasta.
Heat the vegetable oil in a large skillet over medium-high heat.
Remove the feet from each scallop. Sprinkle the scallops with salt and pepper. Add the scallops to the heated skillet, raise the heat to high and sear until golden brown and just firm, 1 to 2 minutes per side; transfer to a plate. This will happen quickly so keep your eye on them so they don't overcook!
Return the skillet to medium-high heat, add the butter and garlic and cook, stirring constantly, until the garlic is lightly toasted, 2 to 3 minutes. Add the lemon juice and season with salt and pepper. Add the cooked pasta and parsley to the skillet and toss to combine.
If needed, add a little of the reserved pasta cooking water to help thin out the sauce so it evenly coats the pasta.
Divide the pasta evenly into bowls and top each bowl with scallops and more parsley.