Here is a list of the series the Brady Kids appeared in both pre- and post- Brady Bunch:

Maureen McCormick:

Bewitched
I Dream of Jeannie
My Three Sons
The Farmer's Daughter
Honey West
Day by Day

Barry Williams:

Run For Your Life
That Girl
The Mod Squad
Here Come The Brides
Dragnet
The Andy Griffith Show
Lancer
Gomer Pyle USMC
The Invaders
Mission: Impossible
Marcus Welby M.D.
Highway To Heaven
Murder She Wrote

Eve Plumb:

The Big Valley
It Takes A Thief
Lassie
Mannix
Gunsmoke
Adam 12
Family Affair
Here's Lucy
The Love Boat
Fantasy Island
The Facts Of Life
That '70's Show

Christopher Knight:

Bonanza
Mannix
Gunsmoke
Day by Day


Mike Lookinland:

Funny Face
The Wonderful World of Disney
Day by Day
Little House On The Prarie

Susan Olsen:

Ironside
Gunsmoke
Julia

Here is a list of the series the Brady Kids appeared in both pre- and post- Brady Bunch:

Maureen McCormick:

Bewitched
I Dream of Jeannie
My Three Sons
The Farmer's Daughter
Honey West
Day by Day

Barry Williams:

Run For Your Life
That Girl
The Mod Squad
Here Come The Brides
Dragnet
The Andy Griffith Show
Lancer
Gomer Pyle USMC
The Invaders
Mission: Impossible
Marcus Welby M.D.
Highway To Heaven
Murder She Wrote

Eve Plumb:

The Big Valley
It Takes A Thief
Lassie
Mannix
Gunsmoke
Adam 12
Family Affair
Here's Lucy
The Love Boat
Fantasy Island
The Facts Of Life
That '70's Show
I can't recall Barry Williams on the Andy Griffith Show or Gomer Pyle.

I don't remember some of these appearances either. I got most of the list from The Brady Bunch Book by Andrew J. Edelstein & Frank Lovece, that came out in 1990, and added a few more that I remembered.

Christopher Knight:

Bonanza
Mannix
Gunsmoke
Day by Day


Mike Lookinland:

Funny Face
The Wonderful World of Disney
Day by Day
Little House On The Prarie

Susan Olsen:

Ironside
Gunsmoke
Julia

Mike Lookinland also appeared in the 1970s blockbuster Movie Towering Inferno with Paul Newman

Maureen was also on Fantasy Island several times. Plus Love Boat and Hardy Boys/Nancy Drew mysteries.

Chris was also in an episode of CHIPs (I have that on tape) and a soap opera or two--oh, and an episode of Happy Days.

Maureen was also on an early episode of Happy Days. She played a girl who, along with a couple of friends, were "using" Richie and his buddies to make their boyfriends jealous.

Eve Plumb also appeared in an episode or two on "One Day at a Time"

I can't recall Barry Williams on the Andy Griffith Show or Gomer Pyle.
I don't remember him in "TAGS" either, but on "GOMER" he had a small role in the tag scene of one of the episodes where the platoon was in Hollywood making a movie. When Gomer & Sgt. Carter walk out of the studio, 2 kids ask them for their autograph and he's one of them.

Here is a list of the series the Brady Kids appeared in both pre- and post- Brady Bunch:


Eve Plumb:

The Big Valley
It Takes A Thief
Lassie
Mannix
Gunsmoke
Adam 12
Family Affair
Here's Lucy
The Love Boat
Fantasy Island
The Facts Of Life
That '70's Show

I don't suppose you have the details of her pre Brady appearances?
so far the only one I've been able to confirm is the one on family affair. I'd like to add the pre Brady ones to her Wikipedia article.

Eve Plumb's Lassie appearance was in 1967. It was a Christmas episode. Her characters' little dog wanders off Christmas Eve. Lassie finds the dog and returns it to her while she and her family are sitting in church.

I don't suppose you have the details of her pre Brady appearances?
so far the only one I've been able to confirm is the one on family affair. I'd like to add the pre Brady ones to her Wikipedia article.
I got this info from The Brady Bunch Book by Andrew J. Edelstein & Frank Lovece. It has a chapter on the filmographies of all the castmembers. I added a few more that I knew of. (Its not a complete list, as people have posted other appearances they've made)

Eve's Here's Lucy appearance was in 1972. She played Lucy's niece, and was with Lucy and Kim at a Donny Osmond performance.

Lucy and Donny Osmond original airdate: November 20, 1972 (During the run of The Brady Bunch)

It's quite remarkable to find out how many major TV shows these kids appeared in during those years. The older Brady kids had extensive careers before the BB, and not just in commercials. Their resumes are impressive.

Some more:

Barry Williams - Three's Company
Do soaps count? I believe he was on General Hospital briefly.

Chris Knight - One Day at a Time
Happy Days
If soaps count, he was on Another World in the early 80's.

I will now research Day by Day. That is the one show mentioned that I never heard of.

Day by Day did a spoof on The Brady Bunch. Florence Henderson, Robert Reed, Maureen McCormick, Chris Knight, Mike Lookinland, and Ann B. Davis were all featured in dream sequence.

Some more:

Barry Williams - Three's Company
Do soaps count? I believe he was on General Hospital briefly.

Chris Knight - One Day at a Time
Happy Days
If soaps count, he was on Another World in the early 80's.

I will now research Day by Day. That is the one show mentioned that I never heard of.
Eve Plumb appeared briefly on Days of our Lives as a patient of Marlena Evans, shortly before Diedra Hall left the show.

I don't remember him in "TAGS" either, but on "GOMER" he had a small role in the tag scene of one of the episodes where the platoon was in Hollywood making a movie. When Gomer & Sgt. Carter walk out of the studio, 2 kids ask them for their autograph and he's one of them.
Yes, right after i replyed to this thread i saw a clip of that scene in another thread on Sitcoms Online. I still can't figure out what episode he was in on TAGS though.