Decent Restaurant Near Marcus Amphitheater- Milwaukee
You will have to venture into the Third Ward, because there is nothing really close to the Marcus. Riptide is in view of Marcus, it isn't a short walk but a doable one. Riptide is OK , the best thing about it is the seating along the river.
Steak fare will be pricey anywhere downtown area. So if your set on steak you'll pay. The Hinterland Gastropub on Erie has a lounge menu that is pretty decent. They also have a very decent wine list. The lounge doesn't take reservations, the main dining room does but that menu is higher end.
Coast is right across from Milwaukee Art Museum. They have a varied menu(didn't see steak).