Can I opt out of an employer's health insurance coverage if they stop paying their share of it?

In January, my employer is making me pay for 100% of my health insurance. They also dropped vision and dental. I am one of the only young people in the firm, and I don't want to be forced to pay a higher premium for reduced coverage. I quoted the most comprehensive plan I could find for me as an individual (including vision/dental), and it's $200 less a month. Can I drop the firm's insurance and just get my own?
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You have to opt out of it during open enrollment. As long as it's open enrollment, yes, you can drop out.
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