Looking at the numbers I posted, I'd like to show my work. Now in some of the segments, Frank is probably just doing the voice, and some might have been produced in one season but broadcast the next.
As Bert: Ernie counts zero fruits, Cave Person Days: Inventing the Window, Ernie tries teaching Ernestine his name (vocal cameo), I Think That It is Wonderful (4)
As Grover: Monsterpiece Theater: The Taming of the Shoe, O'Brien's Fast Food Restaurant, Grover and Sarah talk about the word "quiet", Grover and Torian discuss front and back, two interactions with Zelda, Grover rhymes (7)
As Cookie Monster: Monsterpiece Theater: The Taming of the Shoe, Monsterpiece Theater: Guys and Dolls, zero cookies, Cookie and Diana talk about the word idea, Tara explains information to Cookie, Cookie and Zelda discuss cookies, I Think That It is Wonderful (7)
Bert and Grover also appeared in The Word is No!, but they don't have any dialogue there and probably weren't performed by Frank.
As Bert: Bert and Ernie opposite game, B&E heavy and light game, Cave Person Days: Inventing the trash can, Keep the Park Clean for the Pigeons (4)
As Grover: Monster in the Mirror, Waiter Grover: Airport Restaurant, Waiter Grover: Most Important Meal, Monsterpiece Theater: The Old Man and the C, MT: The Old Man and the C, MT: The King and I, MT: The 400 Blows, MT: The Postman Always Rings Twice, Dial S for Super Grover, Dog Walker, Marshall Grover: Water in the Desert, Grover and Caroline: YOU, AlphaQuest: S (maybe) (11-12)
As Cookie Monster: Monsterpiece Theater: One Flew Over the Cuckoos Nest, MT: The Old Man and the C, MT: The King and I, MT: The 400 Blows, MGT: The Postman Always Rings Twice, Murphy Brownbag (6)
As Grover: Monsterpiece Theater: The Monsters of Venice, MT: The Sun Also Rises, Waiter Grover: Pavlov's Waiter, Super Grover and Super Elmo, Bo Knows, near and far surfing (6)
As Cookie Monster: Three Monsterpiece Theater segments, Two-Headed Monster's vacation, Bo Knows, What is Friend?, Cookie and Prairie show the eyes nose and ears (7)
This season also debuted the celebrity edit of Monster in the Mirror, which has a new ending scene with Grover, though without dialogue, and I'm unsure if Frank Oz performed him in that short scene or not.
- Season 23 - 14 (maybe 18)
As Bert: Calling all pigeons
As Grover: Monsterpiece Theater: Much Ado About Nothing, MT: Waiting for Elmo, Waiter Grover: CH Sounds, pizza delivery, Grover's taxi, flight attendant Grover helps Mr. Johnson get warm, Super Grover: Saving Energy, Singing in the Rain, The Little Monster Who Cried Wolf
As Cookie Monster: Four Monsterpiece Theater segments (and I think this is the season where they re-shot the Allistair Cookie portions of at least four earlier segments, one of which never aired in this form), Cookie Monster's nightmare, nature walk with Prairie Dawn
This season also premieres Adventure, which has Grover, without dialogue, so I am unsure whether Frank performed him in this one or not.
As Bert: Take a Rest, El Timbalo, Stick Out Your Hand and Say Hello, I Gotta Be Clean (4)
As Grover: Take a Rest, El Timbalo, Waiter Grover: Finally a new waiter!, outdoor cafe, Super Grover: crossing the street, Super Grover and Super Annette, MT: Monsters with Dirty Faces, MT: Room at the Top, Grover plays pool with Rick Moranis, Telly shows up and down, Grover lets Jake count millions and millions, here and there lecture (12)
As Cookie Monster: Take a Rest, El Timbalo, six Monsterpiece Theater segments, fast and slow, Annette Benning shows cookies here and there (10)
As Prince Charming: Fairy Tale Today Rapunzel (1)
As a one-shot: The Once and Purple King (1)
As Bert: Ernie catches all the fish, E&B: Headphones, Ernie says Hola, Elmo scares the pigeons, Bert waits for ice cream (4-part sketch) (8)
As Grover: Waiter Grover: Front and back of chair, Guido's Trattoria and Spaghetti Joint, Grover portraits a specialty, Please take a number sir (two different endings), park guitar player, exercise instructor , Super Grover's superhero school, four interactions with Carrington (two of which first aired in season 26), Grover and Kana breathe in air, three interactions with Morgan, bubble poem, Grover Monster's Workout Video, Grover's Curtain, moving Monty's chair (20)
As Cookie Monster: Six Monsterpiece Theater segments (plus one that must have been held over for season 26), Cookie Monster's riddle, important, Telly and Cookie eat fast and slow, Gingerbread Man, three interactions with Jawhara, eight interactions with Lexine (one of which was held over for the next season), Cookie imagines ways to get Prairie Dawn's cookie, the first and last cookie (23)
- Season 26 - 4 (though all are clearly holdovers from season 25.... so 0 here and 35 in season 25)
As Cookie Monster: Monsterpiece Theater: Anyone's Nose, one segment with Lexine (2)
As Grover: Two interactions with Carrington (2)
- Season 27 - 15 (I previously put down 21, not sure if there's something I overlooked tonight or if I messed up previously)
As Bert: Ernie clears the fears, drum experiment, Animals in/on/under, quiet, Ernie plays house (4)
As Grover: Wig salesman, Grover sells clothes, flight attendant Grover provides something to read, at the concession stand, MT: ABCD Blue, Marshall Grover: Fence (6)
As Cookie Monster: Two Monsterpiece Theater segments, Susan Sarandon learns to eat cookies like Cookie Monster, shell game, closing the cookie box (5)
- Season 28 - 17 (I previously counted 29, don't know what I missed counting tonight)
As Bert: Ernie walks forwards and backwards, discovery of air (2)
As Grover: Jordan sings the alphabet for Grover, seven interactions with Samantha, weather report, fifteen seconds to talk about love, fifteen seconds to say an S word, Exit sign, Grover looks for the letter A (13)
As Cookie Monster: Cookie does something unexpected, inside scoop, The Sesame Street Open, Up and Down (remake) (4)
As Bert: Things That I Remember, Bert's Fairy Tales: Sleeping Beauty (2)
As Grover: Waiter Grover tomato surprise, Chicken Castle, take me out of the ballpark, light and dark with Kermit, Theater in the Park: Richard the Last, Super Grover and Super Baby, two interactions with Megan, two segments with Patrick, Samantha counts to 100 (4-part sketch), next to mailbox, Elmo helps Grover with the alphabet, red and blue (13)
As Cookie Monster: Zero Cookies with Gladys Ormphby, cookie painting, Cookie Monster's experiment, blindfold cookie game (4)
As Bert: I Like to Sing, Imagination (remake), Ernie prepares for bed, What's the Name of That Song?, the lost duckie (vocal) (seen in summer reruns of episode 3806, also in an altered season 29 episode in Winter 1999) (5)
As Grover: Hot dog vendor, car rental, Elmo's World: Food, You and You and Me (4)
As Cookie Monster: episode 3804 street scenes, C is for Cookie (remake), Monsterpiece Theater: The Horse Whisperer, Cookie asks Prairie questions, Elmo's World: Food (5)
- Season 31 - I am having trouble determining how many of these are truly Frank Oz, but I'll count what I am most sure of.
As Grover: Telegram, 30 minutes to show surprise (at least 2)
As Grover: Letter of the Day: O (part 2), LOTD: N (part 2)
As Cookie Monster: Ten Letter of the Day segments (10)
As Bert: B&E Dancing Monsters, It's a Circle, Wake Up, frog count to 100, Guess That Animal Sound (5)
As Grover: Five Global Grover segments (5)
- Season 35 - 2 (and some interactions between Grover and kids, don't know how many)
As Grover: some interactions with kids (don't know how many)
As Cookie Monster: The First Time Me Eat Cookie, episode 4075 (2)
- Season 36 - 4 (and again, some interactions between Grover and kids)
As Bert: Sleep, I Love My Toes, Imagining a Dinosaur, Guess What's Next Game (4)
- Season 37 - 6 (and I think an unaired interaction between Grover and a kid)
As Bert: The Ding-Along Song, I Heard the Dog Bark, Breakfast is the Best Meal of the Day (3)
As Grover: Russian Restaurant, Outrageous Makeover: Home Addition (2, plus maybe an unaired kid interaction)
As Grover: 1 Marshall Grover In Front Of (1)
As a one-shot: Mad Men (1)
- Season 41 - 0
- Season 42 - 2
As Grover: Spider-Monster: The Musical (1)
As a one-shot: The Heaviest Catch (1)
As Grover: Coffee Plant, Special (2)
As one-shots: Birdwalk Empire, Upside-Downton Abbey (2)
Compared to when I did this before (without showing my work), there are a few cases where I either miscounted or something (maybe forgot some things). I see that he did a lot more material in season 25 than I counted previously (I'm trying to remember if I counted multi-part segments once or all parts as separate segments).
This took me about two hours. I hope to try to see how many segments he did each season for seasons 10-19, I think season 10 was the last where he regularly did street scenes, but he didn't do many one-shots after that, and most character sketch pages should have all the firsts (though I think some of the season 17-19 Bert sketches still only list the earliest known appearance as opposed to first). Hopefully it won't take me so long.