opengl zoom

I'm putting together a game where all the graphics must be drawn into 240x208 pixels. Depending on my platform, I'd like to be able to zoom into that space so it fits the width of the screen.
I looked at the PinchZoom demo where it looks like zooming is achieved by blit scaling the edgelib logo. I considered drawing my graphics onto such a surface and scaling it to achieve the desired effect, but then I'd have to upload the surface on each frame, which would impact performance. Would it be possible to adjust the zoom by changing the openGL/view settings instead, while retaining the blending I noticed in the PinchZoom approach?
I looked at the PinchZoom demo where it looks like zooming is achieved by blit scaling the edgelib logo. I considered drawing my graphics onto such a surface and scaling it to achieve the desired effect, but then I'd have to upload the surface on each frame, which would impact performance. Would it be possible to adjust the zoom by changing the openGL/view settings instead, while retaining the blending I noticed in the PinchZoom approach?