If Earth had multiple natural satellites (moons) would they all be in the same phase at the same time?

The phase is dictated by their position relative to the sun. Like so.
So, if they’re all at the same position, yes, they’d all be in the same phase. But if their orbits differ, then their appearance to us would differ.

That’d be so cool to have more moons! Think of all that cheese.

@Sarcasm: But wouldn’t they all have to differ, at least slightly? Because in order for their phases to be identical… Wouldn’t their precise location also have to be… Identical? And then wouldn’t they only be one Satellite?

On a related note… I tend to agree about the cheese. It’d have to be a nice odiferous cheese though.

actually, (and i know you are not going to believe me) but earth does have more than one moon. i present to you our 2nd moon ‘Cruithne’. more info: wiki