Cook macaroni according to package directions. Drain and set aside.
Saute green pepper, celery, and onion in hot olive oil in a medium skillet over medium-high heat 5 minutes or until tender.
Combine vegetables, macaroni, mayonnaise, and next 7 ingredients in a large bowl; stir well. Transfer to a greased 1 1/2-quart baking dish. Bake, uncovered, at 325° for 20 minutes. Combine breadcrumbs and margarine; stir well. Sprinkle breadcrumb mixture and paprika over casserole. Bake an additional 10 minutes or until thoroughly heated.