Is it OK to drink alcohol?

Yes No
And of the fruits of the date-palm, and grapes, whence ye derive strong drink and (also) good nourishment. Lo! therein is indeed a portent for people who have sense.
Strong drink and games of chance. Say: In both is great sin.
At the begining of Islam, drinking alcohol was allowed. The prohibition went through stages. Some say it was so to allow those who got used to drinking to easily give it up.
Stage One: Educating people that the harm of drinking wine is greater than its
benefits. "They ask thee concerning wine and gambling. Say: in them is great sin
and some profit for people: But the sin is greater than the profit..." (2: 219)

Stage Two: Encouraging them not to go to prayer intoxicated. "Oh you who
believe! Approach not prayers in a state of intoxication until you can understand
all that you say…” (4: 43)

Stage Three: After understanding and practising the above, the total and decisive
prohibition of wine was declared: “Oh you who believe! Truly intoxicants and
gambling and divination by arrows are an abomination, of Satan's doing: avoid it
in order that you may be successful.” (5: 90)