As we have learned, the Torah prohibits eating ḥametz after midday on the 14th of Nisan, and the Sages extended the prohibition by two hours as a safeguard. Hence, one may eat ḥametz on Erev Pesaḥ until the end of the fourth seasonal hour (i.e., the first third of the day). There are, as is evident from Jewish calendars, two approaches to calculating these hours. According to Magen Avraham, we begin calculating them from dawn; according to the Vilna Gaon, from sunrise. Ideally, one should be stringent and calculate the onset of the prohibition according to Magen Avraham. However, when necessary, since the prohibition against eating ḥametz after the fourth hour is rabbinic, one may be lenient and eat ḥametz until the end of the fourth hour according to Gra’s calculation (above, 3:6).
After four hours, a problem arises for those who customarily refrain from eating kitniyot on Pesaḥ: What can one eat to satisfy his hunger? Ḥametz and kitniyot are forbidden, and even matza is rabbinically forbidden on the 14th of Nisan. We have seen that even matza meal-based cakes and cookies are subject to dispute among poskim. In practice, since this disagreement pertains to a rabbinic prohibition, one may be lenient, though stringency is commendable. According to all opinions, one may eat cooked matza balls.
Egg matza (matza ashira, which includes matza kneaded with oil, wine, or any other fruit juice) may be eaten on Erev Pesaḥ and Pesaḥ according to Sephardic custom, but according to Ashkenazic custom it is forbidden (SA 462:1-4). Nowadays, serious concerns have arisen about the way matza ashira is produced, and according to most poskim, even Sephardic Jews must refrain from matza ashira, even on Erev Pesaḥ after midday (above, 8:1).
Even those whose custom is to eat matza ashira (when produced properly, without any problems) may eat it only until the end of the ninth seasonal hour of the day. With the onset of the tenth hour, three hours before the beginning of the holiday, the Sages forbid eating any sort of baked goods, so that one’s appetite is whet for the matza and festive meal of the Seder. If one is hungry during these hours, he may eat fruit, vegetables, meat, or fish, as long as he is careful to eat a small amount so that he will be hungry in the evening. If one is so sensitive that if he eats meat or some other food in the afternoon he will not be hungry at night, he must plan his meals on Erev Pesaḥ so that he has an appetite when he eats the matza that evening (SA 471:1-2).