Scholar Michael Coogan insists that the rendering "In the beginning God created the heavens and the earth" is grammatically incorrect, according to the original Hebrew reading of Genesis 1:1. He makes this claim in his introductory work to the Old Testament. While the respected translator and scholar Robert Alter departs from the traditional reading of Gen 1:1 and prefers to translate 1:1 with "When God began to create heaven and earth"--one thing I've learned about translation is that one must be careful about stating something in absolute terms that can be understood in more than one way.
For instance, notice what the NET Bible states about Genesis 1:1, which explains why many Bibles do stick with the traditional reading of 1:1:
The translation assumes that the form translated “beginning” is in the absolute state rather than the construct (“in the beginning of,” or “when God created”). In other words, the clause in v. 1 is a main clause, v. 2 has three clauses that are descriptive and supply background information, and v. 3 begins the narrative sequence proper. The referent of the word “beginning” has to be defined from the context since there is no beginning or ending with God.
See the NET Bible for a discussion of some issues that affect the translation of Gen 1:1. But my point is that Coogan too strongly maintains that the reading found in KJV and other Bibles is grammatically incorrect based on the original Hebrew when he should have noted that it's a viable option, even if he disagrees with how others have elected to construe the Hebrew text.