The vote was 7-6 against Sen. Randy Brogdon's Scientific Education and Academic Freedom Act.
Brogdon, R-Owasso, said science teachers in his district fear retribution for bringing up alternative theories on a wide range of subjects, such as evolution and stem cell research.
Sen. Richard Lerblance, D-McAlester, called the measure a subterfuge that would lead to teaching of theories based on religious viewpoints and not science.
"Senate Bill 320 is a wolf dressed in sheep's skin," Lerblance said, predicting it was a first step toward teaching intelligent design in Oklahoma schools.
"This is the biggest case of window dressing that I've seen" and "a direct slap at education," Lerblance added.
The theory of an intelligent design to the universe and life has been advanced to counter court rulings prohibiting the teaching of creationism as science.
Brogdon said he did not mandate anything in his legislation, other than to allow teachers and students to have "an open dialogue on many types of issues."
Sen. Susan Paddack, D-Ada, noted that Brogdon's bill was endorsed by a preacher who spoke to the Senate last week and issued a warning about spreading atheism.
Brogdon said the minister spoke from the heart and his sentiments would probably be supported by "80 percent, probably 90 percent of Oklahomans."
Sen. Jim Halligan, R-Stillwater, was among those voting against the measure.
Halligan objected to a provision he said would allow students to refuse to answer test questions on a subject because they did not believe what was being taught in textbooks.