Running more than one set of speakers in parallel from a single amp can sometimes put a strain on the amp that the amp won't like. This impedance is generally measured in ohms (though it's actually more complicated than that). Do you know if your speakers or amp specify anything about "ohms" or "impedance"?
What speakers and amp are you using?
Doing this can be a problem because of these impedances, but you can also get away with it, especially if you are not driving the speakers to loud volumes. Also, most recent technology amps and receivers will enter a protect mode in the event that you are encountering problems, so you may have an opportunity there to see if you having troubles.
The bottom line is this -- yes, it will work, but you may have amplifier power problems, especially at higher volumes. Personally, I would try it; indeed I have two pairs of speakers connected just as described to an older Kenwood receiver for "family room" and "patio" duty. No problems whatsoever.
Good luck!