Guard and Reserve Readiness and Retention Act of 2004

Guard and Reserve Readiness Retention Act of 2004 - Makes eligible for retired pay non-regular service reserve personnel who obtain the following age and years of reserve service: (1) 60 and 20; (2) 59 and 22; (3) 58 and 24; (4) 57 and 26; (5) 56 and 28; (6) 55 and 30; (7) 54 and 32; and (8) 53 and 34. (Currently, only those obtaining 60 years of age with 20 years of such service are eligible.)

Removes the requirement that members of the Selected Reserve and the Individual Ready Reserve may be eligible for benefits under TRICARE (a Department of Defense managed health care program) only if such members: (1) are eligible unemployment compensation recipients; or (2) are not eligible for health care benefits under any employer-sponsored health benefits plan. Makes such eligibility permanent (currently terminates December 31, 2004).

Directs the Secretary of the military department concerned to pay the applicable premium to continue in force any qualified health plan coverage for a reserve member (and his or her dependents) while the member is serving on active duty pursuant to a call or order issued during a war or national emergency declared by the President or Congress. Requires the continuation of COBRA coverage during such period. Prohibits simultaneous coverage under both the qualified health plan and TRICARE.