As near as I can put together, the following Invader appearences are in-order of publishing dates.

Avengers Vol. 1, #71 -- The first appearence of the Invaders

Invaders Giant Size#1

Invaders#1-41 -- The ongoing series!

Invaders Annual #1

Marvel Premiere#29-30 -- The Libert Legion must save the Invaders! Crosses over into the regular Invaders ongoing.

What If? Vol. 1, #4 -- An out-of-continuity "What If the Invaders Kept Together After World War II?" issue

Fantastic Four Annual #11 -- The Foursome meet an alternate realities Invaders

Marvel Two-In-One Annual #1 -- Continued from FF Annual#11, the Liberty Legion guest-star

Marvel Two-In-One #79 -- Featuring the Thing and the Liberty Legion's Blue Diamond.

Captain America Vol. 1, #253-254 -- Cap travels back to England and discovers that Baron Blood is still alive. Death of the original Union Jack, first appearence of the third

Marvel Comics Presents #34 -- The final fate of Thin Man and Agent Axis

Marvel Comics Presents #89 -- A solo Spitfire tale

Knights of the Pendragon Vol. 1, #7-18 -- The third Union Jack gains mystical abilities and fights alongside the Pendragon squad

Knights of the Pendragon Vol. 2, #1-15 -- Continuing from the previous volume. Union Jack appearences throughout

Namor the Sub-Mariner #12 -- BIG issue. Invaders meet again in present day, Spitfire de-ages from a sixty year old woman to a 16 year old teenager. Original Human Torch loses powers

Namor the Sub-Mariner Annual #1 -- Small Invaders section

Namor the Sub-Mariner Annual #2 -- A solo shot featuring Spitfire

Marvel Super-Heroes Vol. 2, #4 -- Another Spitfire tale

Marvel Super-Heroes Vol. 2, #8 -- Namor meets the daughter of the Liberty Legion's Red Raven

Thor Corps #2

The Invaders Mini-Series
#1
#2
#3
#4

Marvel Universe
#1 -- Flashback tale that has the Invaders going up against HYDRA in the latter days of World War II
#2
#3

Heroes for Hire #12 -- Though the whole stint of this series featured a powerless Jim Hammond (the Human Torch), this issue had him partially re-gain his decade-old fire control power

Captain America: Sentinel of Liberty #2-4 -- The Nazis have made an alliance with Atlantis, and now the Invader must defeat both sides--and don't forget that army of Human Torch clones sent out to kill the heroes

Union Jack Mini Series
#1 -- Re-introduces Union Jack III, Spitfire, and more
#2
#3 -- Kenneth Chricton, grandson of the original Union Jack, dies