The previous owners cut a "window" into a wall looking into the kitchen. It's almost like a half finished idea and we want to finish it by making it a bar/counter space. Is it safe to install granite on a plain old wall? I assume we will need plywood/corbels/steel brackets to support the overhang but will a relatively free standing wall support the weight? If not, would extra support like columns or legs fit the bill?

Can you post a picture? Hard to say about the wall strength since we do not know how the previous owner built a base. It should be OK but the over hang can't be more than a few inches, otherwise leaning on the counter would creat too much leverage and break it loose.