While there is no scriptural command for all people of today to be vegetarians, the Bible does have quite a bit to say about eating meat, or abstaining from it.
Initially, Adam and Eve, the two first people, and all of their offspring, were vegetarians. They were told by God what they were allowed to eat, and meat was not included.
Genesis 1:29-30 (NASB)
Then God said, "Behold, I have given you every plant yielding seed that is on the surface of all the earth, and every tree which has fruit yielding seed; it shall be food for you; and to every beast of the earth and to every bird of the sky and to every thing that moves on the earth which has life, I have given every green plant for food"; and it was so.
Later on, after the flood of Noah, God allowed people to begin to eat meat.
Genesis 9:3 (NASB)
"Every moving thing that is alive shall be food for you; I give all to you, as I gave the green plant."
Many Christians believe that with the radical alteration of the environment due to the global flood, vegetables were in general no longer as healthy nor as plentiful, thus making the consumption of animal products necessary for human survival. The Bible does not give us a specific reason why God chose to allow people to eat meat at this point. We only know for certain that He did.
In the book of Daniel, the prophet Daniel, when taken into exile with the Jews by the king of Babylon, is selected to become a special servant of the king. He is provided with choice meats and other foods, the best of the best, and he chooses to abstain from eating them, preferring vegetables.
Daniel 1:8-15 (NASB)
Daniel made up his mind that he would not defile himself with the king's choice food or with the wine which he drank; so he sought permission from the commander of the officials that he might not defile himself... "Please test your servants for ten days, and let us be given some vegetables to eat and water to drink. Then let our appearance be observed in your presence and the appearance of the youths who are eating the king's choice food; and deal with your servants according to what you see." So he listened to them in this matter and tested them for ten days. At the end of ten days their appearance seemed better and they were fatter than all the youths who had been eating the king's choice food.
The reason for Daniel's abstinence from meats is not clearly given. As far as the scriptures reveal, he was not under any religious obligation to refuse to eat beef or chicken or lamb, but he was certainly commanded by God not to eat meat with blood still in it (Leviticus 3:17), and not to eat certain meats such as pork (Leviticus 11:7). We don't know if rare (bloody) steak was one of the "choice foods", or if there was an abundance of pork on the king's table, or if Daniel simply thought a vegetable diet would be healthier. So we don't know for certain why he abstained.
In the book of Romans, Paul makes it clear that becoming a vegetarian or not becoming one is a choice that Christians are permitted to make.
Romans 14:2-4 (NASB)
One person has faith that he may eat all things, but he who is weak eats vegetables only. The one who eats is not to regard with contempt the one who does not eat, and the one who does not eat is not to judge the one who eats, for God has accepted him. Who are you to judge the servant of another? To his own master he stands or falls; and he will stand, for the Lord is able to make him stand.
The principle in making the decision to eat meat or not to eat meat is stated in verse 14:
I know and am convinced in the Lord Jesus that nothing is unclean in itself; but to him who thinks anything to be unclean, to him it is unclean.
Paul also makes it clear that it is best to modify one's own behavior to account for the restrictions that only exist in other people's minds if, by exercising our freedom, we cause our brother to stumble in his faith.
It is good not to eat meat or to drink wine, or to do anything by which your brother stumbles.
1 Corinthians 8:13
Therefore, if food causes my brother to stumble, I will never eat meat again, so that I will not cause my brother to stumble.
He puts things in perspective in 1 Corinthians 8:8:
But food will not commend us to God; we are neither the worse if we do not eat, nor the better if we do eat.
So we see that in Christianity, eating meat is a choice that we are free to make. However, we should remember our neighbors in this choice-making, and be considerate of other people's consciences.
God bless you in your pursuit of Truth.