The study has 2 parts, called Phase I and Phase II. In the Phase I portion, participants will be treated with 1 of 4 dose combinations of capecitabine, bevacizumab, and erlotinib hydrochloride, along with radiation therapy. The dose level of capecitabine and erlotinib hydrochloride will change during Phase I, but the dose levels of bevacizumab and radiation therapy is the same for all participants. The first group of participants will be given the lowest dose combination. If that group does not experience intolerable side effects, the next group of participants will be enrolled at a higher dose level. This will continue until the highest tolerable dose level of the study drug and radiation therapy combination is found (called the maximum tolerated dose, or MTD).