Hmmm, that's tricky. Hero's feast lists its duration as "instantaneous," but then, after you eat the feast you get "benefits" that last 24 hours. I'm not sure the "benefits" count as a spell effect in the traditional sense, but then, I'm not sure what else they would count as?
I guess the answer is the same as the answer to "Can you dispel the benefits of hero's feast?"
I guess the answer is the same as the answer to "Can you dispel the benefits of hero's feast?"