How are Christians supposed to treat the Old Testament?

Whenever anyone quotes something kooky from the Bible it is often the Old Testament that the passages are found in. What is supposed to be invalidated by the New Testament? Is the OT pretty much just a collection of stories to them?

Good question. Some folks take the OT very seriously. It makes me roll my eyes when they, for example, quote Leviticus on homosexuality being an abomination, but conveniently omit the fact that this code is full of abominations and no-no’s such as women wearing men’s clothes, sowing two crops in the same fields, anyone wearing blended fabrics, working on the Sabbath and so on.
Some also take the creation story in Genesis quite literally as well.

I think the above folks are mostly fundamentalists, but it’s not exclusive to them.

I have not answered your question very well. But I am waiting to see if someone else can shed more light on this.

I think it’s because of the reason gave in the last sentence of this web page.
But some say this doesn’t cut it, since Jesus says:

“Do not think that I came to destroy the Law or the Prophets. I did not come to destroy but to fulfill” (Matthew 5:17).

I meant to write last paragraph, not last sentence.

Depends on the Christian, really. Fundamentalists stand by the OT stories as much as the NT ones, ignoring glaring contradictions in tone and theme between the two, and justifying many of their own prejudices with its strictures. More, shall we say, thoughtful and introspective Christians tend to regard them as folklore-style tales of the Jewish people, with moral lessons to be learned, though not literally followed (see: those Leviticus examples cited above).

Take the book of Job: it’s a classic examination of the whole “How does God let bad things happen?” problem, though many Christians don’t actually believe that God would just let this poor Job fellow get his ass handed to him over and over, just to test his faith! I wouldn’t want to follow a God like that, anyway.

You’ll always find different interpretations re. whether Jesus came more to supersede the laws of the past, or to fulfill them. The quote above seems to indicate it pretty clearly, but there’s other indications that he intended to overthrow part of what had come before. Again, there’s plenty of contradictory material to sift through. But if you’re willing to accept the Bible as the imperfect record that it is, it’s not necessary to reject it entirely because of that.

What is the official stance of the Catholic church?

They are of the position that you don’t follow many of the laws of the OT, such as a man who lies with a man should be put to death or the prohibition against eating pork, but one has to wonder if this is to make the religion more acceptable for the masses. The church also doesn’t follow some NT laws, such as shaving a woman’s head if she refuses to cover her head in church.

Simple one-size-fits-all answer: It contains the history of God’s dealings with antediluvial man and the Children of Israel/Jews, the Chosen People, which provides the necessary background and underlying concepts for understanding His dealings with all mankind through Jesus Christ and His disciples. To what extent the theology and teachings of the Old Testament are continued, fulfilled, supplemented, and/or replaced by those of the New, is hotly debated not only between but within Christian denominations.

From the Catechism of the Catholic Church:

But lest there be literalists among the faithful, the Catechism opens a big loophole:

A very similar question was asked in GD, recently, that got some decent responses before wandering astray:
OT Irrelevant to Christains?

There’s an interesting point of comparison in the New Testament. In Acts 15 (you’ll also find a somewhat different perspective in several of Paul’s letters) the first-generation church is starting to get a responsive hearing from non-Jews; and that raises the question, are Gentile converts to be circumcised and obey the kosher laws of the Torah?
This was not an easy question, because right behind it was whether Jewish Christians and non-Jewish Christians could celebrate the Lord’s Supper together if some of them weren’t keeping kosher.
Anyhow, the result was interesting: “we should not trouble those Gentiles who are turning to God, but we should write to them to abstain only from things polluted by idols and from fornication and from whatever has been strangled and from blood. For in every city, for generations past, Moses has had those who proclaim him, for he has been read aloud every sabbath in the synagogues.” (Acts 15:19-21, New Revised Standard Version)
Which is to say, an attempt was made to respect the intent of the laws of the Torah, without assuming that all of them apply directly to Gentiles. (My impression is that much Jewish interpretation would take a similar approach.)
In my own tradition (Lutheran), theologians work with the idea that there is not necessarily any one-size-fits-all civil law; that different cultures need to approach “law” with similar goals, but the details may differ. And that many of the commandments of the Torah were given specifically to organize the civil life of the people of Israel; in Luther’s terms, “the Jews’ Saxon Code.” Appropriate and admirable in context; not necessarily applicable directly to other communities.
So of course from that point things get complicated. What applies directly, and what does not? An earlier poster cited the current Roman Catholic Catechism, which makes excellent points. I don’t see easy answers. We make mistakes. And living with ambiguity on something this important can be very uncomfortable.

Disclaimer: I’m not a theologian, of any stripe.

According to a PBS mini-series on early Christianity, many of these decisions were made after Jesus “left the building.” Some were even made after all the Disciples were dead. For example, many early Christians believed that only Jews could convert to Christianity. For them, there were no doubts about circumcision or keeping Kosher. For those who believed any ol’ riffraff could join up, eventually circumcision and Kosher were booted off the wagon. The big dividing line was in the treatment of sin. I only vaguely understand the Jewish way of atonement; I’ll leave that to somebody else. There is still a variety of ways to understand Christ’s forgiveness of sins, but it comes down to “Jesus died to atone for our sins.”

I’m outa here. I got a ball game to watch.