Heat oven to 350° F. Toss the bread crumbs, butter, and ¼ teaspoon each salt and pepper on a rimmed baking sheet. Bake, tossing once, until golden brown, 4 to 6 minutes. Let cool, then toss with the parsley.
Meanwhile, steam the green beans in 1 inch of water until tender, 3 to 5 minutes; drain. Transfer to a large bowl and toss with the olives, mustard, 1 tablespoon of the oil, and ¼ teaspoon each salt and pepper.
Heat the remaining tablespoon of oil in a large nonstick skillet over medium-high heat. Season the tilapia with ¼ teaspoon each salt and pepper and cook, in 2 batches, until opaque throughout, 2 to 3 minutes per side.
Serve the tilapia sprinkled with the bread crumbs, with the green beans and lemon wedges on the side.