Interim Medical Coverage for the Unemployed Act of 1983 - Provides for a voluntary State program (with 90 percent Federal funding) of health insurance or medical coverage for unemployment insurance recipients (and family members) who choose to participate. Provides that States shall contribute through deductions from unemployment compensation payments.

Prohibits Federal contributions for an individual participant for more than one year.

Directs the Secretary of Health and Human Services to establish weekly premiums in each State.

Permits States to provide coverage through private insurers, health maintenance organizations, or other State programs.

Authorizes appropriations. Prohibits obligation of funds if a previous fiscal year's unemployment rate was six percent or lower.

Amends the Internal Revenue Code to require employer-provided group health plans to provide for open enrollment of spouses of unemployed individuals in order for employer contributions to qualify as a tax-deductible business expense.