It is worth noting at this point that I am only considering open era debuts, some listed players would have played in these events before that time. As such, I present the most debutantes ever in a draw, for 1968 RG, which had 134.
1968
Roland Garros 1968
Colin DIBLEY (1st Round, #35, 23y 256d)
Francois JAUFFRET (5th Round, #20, 26y 114d)
Georges GOVEN (3rd Round, #56, 20y 36d)
Ilie NASTASE (3rd Round, #1, 21y 318d)
Ivan MOLINA (2nd Round, #40, 21y 351d)
Jairo VELASCO (2nd Round, #49, 21y 24d)
Jan KODES (2nd Round, #5, 22y 93d)
John ALEXANDER (4th Round, #8, 16y 332d)
Manuel ORANTES (2nd Round, #2, 19y 115d)
Mark COX (4th Round, #13, 24y 333d)
Marty RIESSEN (2nd Round, #11, 26y 181d)
Onny PARUN (2nd Round, #19, 21y 48d)
Patrick PROISY (3rd Round, #23, 18y 264d)
Phil DENT (1st Round, #17, 18y 107d)
Ray MOORE (3rd Round, #34, 21y 282d)
Tomas KOCH (Quarterfinal, #24, 23y 22d)
Zeljko FRANULOVIC (5th Round, #33, 20y 354d)
Abe SEGAL (3rd Round, #275, 37y 226d)
Alex METREVELI (2nd Round, #9, 23y 212d)
Alexander MARCIAL (2nd Round, #262, 19y 63d)
Alfredo ACUNA (2nd Round, #-, 21y 192d)
Allan STONE (4th Round, #38, 22y 231d)
Allen FOX (3rd Round, #-, 28y 344d)
Alvaro PENA (2nd Round, #-, 27y 241d)
Andres GIMENO (Semifinal, #49, 30y 305d)
Ashley COOPER (3rd Round, #278, 31y 262d)
Barry GERAGHTY (2nd Round, #-, )
Barry PHILLIPS-MOORE (3rd Round, #60, 30y 330d)
Bernard BOUTBOUL (1st Round, #-, )
Bernard DETROYE (2nd Round, #-, 24y 86d)
Bernard MONTRENAUD (3rd Round, #265, 24y 66d)
Bernard PAUL (2nd Round, #-, 24y 50d)
Bob CARMICHAEL (5th Round, #55, 27y 334d)
Bob GILTINAN (3rd Round, #56, 19y 55d)
Bob HEWITT (4th Round, #34, 28y 143d)
Bob HOWE (2nd Round, #-, 42y 308d)
Bob MAUD (4th Round, #57, 21y 294d)
Bobby WILSON (3rd Round, #-, 32y 195d)
Boro JOVANOVIC (Quarterfinal, #62, 28y 226d)
Brian FAIRLIE (3rd Round, #24, 19y 353d)
Bronislaw LEWANDOWSKI (3rd Round, #-, 20y 275d)
Carlos-Alberto FERNANDES (2nd Round, #-, )
Christian DUXIN (2nd Round, #-, 25y 345d)
Claude DE GRONCKEL (3rd Round, #-, 25y 13d)
Cliff RICHEY (5th Round, #16, 21y 153d)
Colin STUBS (3rd Round, #274, 27y 96d)
Daniel CONTET (2nd Round, #245, 24y 212d)
David LLOYD (2nd Round, #128, 20y 150d)
Detlef HERDY (2nd Round, #-, 26y 233d)
Dick CREALY (4th Round, #36, 23y 257d)
Dimitri STURDZA (4th Round, #202, 29y 206d)
Eduardo CRUZ (2nd Round, #179, )
Eduardo GOROSTIAGA (2nd Round, #288, )
Eduardo ZULETA (3rd Round, #-, 32y 198d)
Eric DROSSART (2nd Round, #-, 26y 102d)
Ferenc KOMAROMY (2nd Round, #-, 31y 227d)
Fernando GENTIL (3rd Round, #222, 18y 82d)
Frank TUTVIN (2nd Round, #-, 22y 283d)
Fred STOLLE (3rd Round, #30, 29y 239d)
Frew MCMILLAN (3rd Round, #39, 26y 14d)
Gaetano DI MASO (1st Round, #-, 23y 85d)
Georges DENIAU (2nd Round, #-, 35y 162d)
Gerald BATTRICK (5th Round, #59, 21y 6d)
Gerard PILET (3rd Round, #-, 34y 263d)
Giuseppe MERLO (2nd Round, #158, 40y 239d)
Herb FITZGIBBON (5th Round, #128, 25y 324d)
Inge BUDING (4th Round, #-, 26y 145d)
Ion TIRIAC (Quarterfinal, #55, 29y 26d)
Isao WATANABE (2nd Round, #274, 26y 192d)
Istvan GULYAS (5th Round, #128, 36y 235d)
Jacques THAMIN (2nd Round, #137, 16y 8d)
Jaidip MUKERJEA (2nd Round, #120, 26y 43d)
Jaime PINTO-BRAVO (3rd Round, #73, 28y 238d)
Jan KUKAL (3rd Round, #115, 25y 263d)
Jean-Baptiste CHANFREAU (2nd Round, #80, 21y 136d)
Jean-Claude BARCLAY (2nd Round, #218, 25y 155d)
Jean-Claude MOLINARI (2nd Round, #-, 36y 282d)
Jean-Loup ROUYER (3rd Round, #133, 22y 302d)
Jean-Pierre COURCOL (3rd Round, #-, 24y 76d)
Jean-Pierre OLIVIER (2nd Round, #365, )
Jim MOORE (2nd Round, #254, 30y 15d)
John BARRETT (2nd Round, #-, 37y 50d)
John BARTLETT (1st Round, #93, 20y 76d)
Jose-Edison MANDARINO (4th Round, #81, 27y 69d)
Joseph MATEO (2nd Round, #-, 33y 66d)
Juan GISBERT (2nd Round, #32, 26y 59d)
Ken ROSEWALL (Winner, #2, 33y 215d)
Lancelot LUMSDEN (2nd Round, #-, 27y 216d)
Lars OLANDER (3rd Round, #-, 25y 339d)
Lew HOAD (2nd Round, #-, 33y 194d)
Marco GILARDELLI (2nd Round, #-, 21y 123d)
Michel LECLERCQ (3rd Round, #-, 27y 234d)
Mike SANGSTER (2nd Round, #-, 27y 265d)
Milan HOLECEK (4th Round, #71, 24y 223d)
Nicky KALOGEROPOULOS (3rd Round, #108, 23y 104d)
Nicola PIETRANGELI (2nd Round, #271, 34y 267d)
Nikki SPEAR (3rd Round, #78, 24y 101d)
Norman PERRY (2nd Round, #-, 30y 25d)
Pancho GONZALES (Semifinal, #109, 40y 28d)
Pancho GUZMAN (2nd Round, #-, 22y 9d)
Patrice BEUST (2nd Round, #308, 23y 272d)
Patricio CORNEJO (4th Round, #65, 23y 361d)
Patricio RODRIGUEZ (2nd Round, #133, 29y 166d)
Patrick HOMBERGEN (2nd Round, #115, 21y 267d)
Paul HUTCHINS (4th Round, #-, 23y 58d)
Peter POKORNY (2nd Round, #221, 27y 313d)
Peter SZOKE (1st Round, #47, 20y 298d)
Petr STROBL (3rd Round, #-, 27y 83d)
Petre MARMUREANU (4th Round, #-, 26y 348d)
Pierre DARMON (4th Round, #-, 34y 142d)
Pierre JAUFFRET (2nd Round, #-, 30y 314d)
Pierre JOLY (2nd Round, #244, 22y 111d)
Ramanathan KRISHNAN (2nd Round, #136, 31y 54d)
Ray KELDIE (2nd Round, #113, 22y 136d)
Ray RUFFELS (5th Round, #27, 22y 71d)
Richard HAWKES (2nd Round, #318, 27y 186d)
Richard RUSSELL (1st Round, #-, 22y 267d)
Rod LAVER (Final, #3, 29y 299d)
Rohan SUMMERS (2nd Round, #-, )
Roy EMERSON (Quarterfinal, #12, 31y 213d)
Sergei LIKHACHEV (2nd Round, #194, 28y 75d)
Sergio PALMIERI (2nd Round, #-, 22y 186d)
Sergio TACCHINI (2nd Round, #-, 29y 275d)
Sever DRON (3rd Round, #-, )
Tadeusz NOWICKI (2nd Round, #119, 21y 330d)
Terry ADDISON (2nd Round, #100, 22y 142d)
Terry RYAN (4th Round, #100, 26y 37d)
Tom EDLEFSEN (2nd Round, #94, 26y 173d)
Torben ULRICH (3rd Round, #96, 35y 244d)
Viktor KAZAKEVICH (2nd Round, #-, 17y 118d)
Wieslaw GASIOREK (4th Round, #504, 32y 143d)
Wilhelm BUNGERT (2nd Round, #144, 29y 64d)
William ALVAREZ (2nd Round, #-, 33y 172d)
Yves CHRISTIAEN (3rd Round, #-, )
Zlatko IVANCIC (2nd Round, #662, )
Wimbledon 1968
Bob LUTZ (1st Round, #15, 20y 305d)
Cliff DRYSDALE (3rd Round, #13, 27y 36d)
Ismail EL SHAFEI (2nd Round, #34, 20y 227d)
Roger TAYLOR (2nd Round, #11, 26y 260d)
Stan SMITH (2nd Round, #3, 21y 198d)
Tom OKKER (Quarterfinal, #3, 24y 129d)
Alan MILLS (1st Round, #-, 32y 239d)
Alex OLMEDO (3rd Round, #190, 32y 100d)
Arthur ASHE (Semifinal, #2, 24y 356d)
Bill BOWREY (2nd Round, #162, 24y 188d)
Butch BUCHHOLZ (Quarterfinal, #156, 27y 288d)
Charlie PASARELL (2nd Round, #35, 24y 139d)
Clark GRAEBNER (Semifinal, #45, 24y 239d)
Clay ILES (2nd Round, #-, 25y 206d) [LL]
Dennis RALSTON (Quarterfinal, #115, 25y 339d)
Derek SCHRODER (1st Round, #214, 28y 66d)
Donald DELL (1st Round, #-, 30y 15d)
Eugene SCOTT (1st Round, #122, 30y 186d)
Francisco CASTILLO (1st Round, #-, 25y 59d) [LL]
Geoff BLUETT (2nd Round, #-, 27y 42d)
Gordon FORBES (1st Round, #-, 34y 132d)
Graham STILWELL (2nd Round, #62, 22y 227d)
Graydon GARNER (2nd Round, #272, 22y 362d)
Hans-Joachim PLOETZ (1st Round, #65, 24y 125d)
Haroon RAHIM (1st Round, #44, 18y 229d)
Jan LESCHLY (2nd Round, #-, 27y 293d)
Jim MCMANUS (1st Round, #90, 27y 288d)
Jim OSBORNE (2nd Round, #211, 23y 149d)
John BROWN (1st Round, #-, 27y 354d)
John NEWCOMBE (4th Round, #1, 24y 38d)
Jorgen ULRICH (2nd Round, #-, 32y 316d)
Jose-Luis ARILLA (2nd Round, #-, 27y 118d)
Jurgen FASSBENDER (1st Round, #31, 20y 32d)
Keith CARPENTER (1st Round, #-, 26y 332d)
Keith WOOLDRIDGE (1st Round, #-, 24y 250d)
Ken FLETCHER (2nd Round, #-, 28y 16d)
Koji WATANABE (1st Round, #-, 26y 163d)
Luis AYALA (1st Round, #482, 35y 288d)
Manuel SANTANA (3rd Round, #145, 30y 53d)
Mike DAVIES (1st Round, #-, 32y 175d)
Niki PILIC (1st Round, #12, 28y 309d)
Ove BENGTSON (3rd Round, #43, 23y 86d)
Owen DAVIDSON (1st Round, #73, 24y 270d)
Peter CURTIS (1st Round, #235, 22y 305d)
Pierre BARTHES (2nd Round, #57, 26y 291d)
Premjit LALL (1st Round, #105, 27y 254d)
Raul PERALTA (1st Round, #-, 28y 14d) [LL]
Robert HAILLET (1st Round, #-, 36y 281d)
Roger BECKER (1st Round, #-, 34y 147d)
Ron HOLMBERG (1st Round, #-, 30y 156d)
Roy BARTH (1st Round, #107, 21y 92d)
Stanley MATTHEWS (1st Round, #-, 22y 222d)
Tomas LEJUS (1st Round, #-, 26y 307d)
Tony PALAFOX (1st Round, #-, 32y 65d)
Tony ROCHE (Final, #8, 23y 44d)
Vladimir KOROTKOV (3rd Round, #113, 20y 67d)
Warren JACQUES (1st Round, #-, 30y 114d)
US Open 1968
Dick STOCKTON (2nd Round, #8, 17y 197d)
Erik VAN DILLEN (1st Round, #36, 17y 194d)
Jaime FILLOL (2nd Round, #14, 22y 93d)
Jeff BOROWIAK (3rd Round, #20, 18y 343d)
Sherwood STEWART (1st Round, #60, 22y 90d)
Tom GORMAN (1st Round, #10, 21y 259d)
Tom LEONARD (1st Round, #34, 20y 50d)
Alberto CARRERO (1st Round, #-, 19y 364d)
Allen QUAY (1st Round, #-, 32y 247d)
Armistead NEELY (1st Round, #144, 21y 169d)
Barry MACKAY (1st Round, #318, 32y 7d)
Butch SEEWAGEN (1st Round, #87, 22y 83d)
Chauncey STEELE (1st Round, #-, 24y 201d)
Chris BOVETT (1st Round, #373, 22y 253d)
Chuck MCKINLEY (3rd Round, #-, 27y 243d)
Cliff MONTGOMERY (1st Round, #-, )
Dan BLECKINGER (2nd Round, #616, 21y 100d)
Dan O'BRYANT (2nd Round, #-, )
Dick DELL (2nd Round, #98, 20y 340d)
Dick KNIGHT (1st Round, #-, 32y 299d)
Frank PARKER (2nd Round, #-, 52y 224d)
Frank ROBBINS (1st Round, #182, 18y 82d)
George TAYLOR (1st Round, #248, 18y 122d)
Humphrey HOSE (1st Round, #125, 21y 123d)
Ian CROOKENDEN (2nd Round, #140, 24y 269d)
James PARKER (1st Round, #-, 25y 183d)
Joaquin LOYO-MAYO (3rd Round, #99, 23y 19d)
John SHARPE (2nd Round, #-, 29y 111d)
Karl COOMBES (1st Round, #162, 20y 261d)
Lenny SCHLOSS (2nd Round, #-, )
Lew GERRARD (2nd Round, #-, 30y 154d)
Mal ANDERSON (3rd Round, #125, 33y 188d)
Marcelo LARA (3rd Round, #59, 20y 334d)
Ned WELD (2nd Round, #1299, )
Pancho SEGURA (3rd Round, #355, 47y 76d)
Paul CRANIS (1st Round, #-, 33y 148d) [LL]
Paul GERKEN (3rd Round, #35, 18y 172d)
Paul SULLIVAN (1st Round, #-, 27y 141d)
Peter BURWASH (1st Round, #240, 23y 206d)
Peter FISHBACH (2nd Round, #272, 21y 6d)
Robert MCKINLEY (3rd Round, #106, 18y 29d)
Robert PERRY (1st Round, #-, 35y 174d)
Ron GOLDMAN (1st Round, #-, 24y 307d)
Sam GIAMMALVA (2nd Round, #189, 34y 37d)
Stanley PASARELL (1st Round, #270, 20y 205d)
Thomas MOZUR (2nd Round, #-, 20y 353d)
Victor Elias SEIXAS (2nd Round, #-, 44y 11d)
William HARRIS (1st Round, #-, 21y 233d)
William TYM (1st Round, #-, 28y 155d)
1969
Australian Open 1969
Adriano PANATTA (1st Round, #4, 18y 200d)
Geoff MASTERS (2nd Round, #42, 18y 128d)
Ross CASE (2nd Round, #14, 17y 85d)
Syd BALL (1st Round, #63, 18y 1d)
Alvin GARDINER (1st Round, #90, 17y 348d)
Anthony HAMMOND (1st Round, #251, 18y 315d)
Harold HUNT (2nd Round, #-, )
Ian FLETCHER (1st Round, #56, 20y 55d)
John COOPER (2nd Round, #66, 22y 83d)
Marc BOLLE (1st Round, #-, 19y 215d)
Massimo DI DOMENICO (2nd Round, #199, 23y 42d)
Piero TOCI (2nd Round, #175, 19y 210d)
Pietro MARZANO (2nd Round, #252, 19y 149d)
Rod BRENT (2nd Round, #-, )
Sutarjo SUGIARTO (1st Round, #-, 31y 344d)
Trevor FANCUTT (1st Round, #355, 34y 199d)
Vittorio CROTTA (1st Round, #-, 22y 289d)
Roland Garros 1969
Mike ESTEP (1st Round, #59, 19y 318d)
Aleksandr IVANOV (1st Round, #-, 24y 52d)
Andrzej LICIS (1st Round, #-, )
Davor STOLCER (1st Round, #-, )
Eugenio CASTIGLIANO (1st Round, #145, 23y 117d)
Ezio DI MATTEO (1st Round, #151, 20y 212d)
Francois PIERSON (1st Round, #-, 24y 201d)
Hans NERELL (2nd Round, #-, 24y 249d)
Hans-Jurgen POHMANN (2nd Round, #30, 22y 11d)
Henry FAUQUIER (1st Round, #-, 27y 154d)
Hussain AKBARI (1st Round, #318, )
Martin MULLIGAN (3rd Round, #44, 28y 229d)
Michael BELKIN (1st Round, #128, 23y 339d)
Michael HICKEY (1st Round, #-, )
Mieczyslaw RYBARCZYK (1st Round, #273, 27y 276d)
Stefan KOUDELKA (3rd Round, #-, 24y 102d)
Taghi AKBARI (1st Round, #146, )
Viktor PALMAN (1st Round, #-, )
Vladimir ZEDNIK (2nd Round, #43, 22y 122d)
Zan GUERRY (2nd Round, #105, 20y 110d)
Wimbledon 1969
John PAISH (1st Round, #80, 29y 99d)
Allan MCDONALD (1st Round, #217, 18y 119d)
John CLIFTON (1st Round, #243, 23y 130d)
Julian KRINSKY (1st Round, #-, )
Keishiro YANAGI (1st Round, #274, 28y 126d) [LL]
Rayno SEEGERS (1st Round, #163, 17y 119d)
William HIGGINS (1st Round, #115, 27y 89d)
US Open 1969
Roscoe TANNER (1st Round, #4, 17y 318d)
Armando CORNEJO (1st Round, #65, 25y 85d)
Bailey BROWN (1st Round, #355, 26y 77d)
Brian CHENEY (1st Round, #-, 21y 272d)
Edward HOEHN (1st Round, #-, 27y 218d)
Jasjit SINGH (2nd Round, #89, 21y 207d)
John HAMMILL (1st Round, #-, 27y 6d) [LL]
Larry TURVILLE (1st Round, #210, 20y 86d)
Luis-Augusto GARCIA (1st Round, #-, )
Martin CARLSTEIN (1st Round, #-, 27y 103d)
Max SENIOR (1st Round, #276, 27y 178d)
Michael SPRENGELMEYER (1st Round, #-, 23y 55d)
Miguel OLVERA (1st Round, #711, 29y 291d)
Pat CRAMER (1st Round, #95, 22y 162d)
Rauty KROG (1st Round, #238, 24y 202d)
Richard N LEACH (2nd Round, #-, 29y 178d)
Robert POTTHAST (1st Round, #-, )
Rudy HERNANDO (1st Round, #151, 30y 83d)
Woody BLOCHER (2nd Round, #156, 18y 5d)
1970
Australian Open 1970
Allan SHAPTER (1st Round, #-, 28y 82d)
Frank SEDGMAN (2nd Round, #237, 42y 120d)
Geoff POLLARD (1st Round, #-, 36y 10d)
Ian BIDMEADE (1st Round, #-, )
Ken STUART (2nd Round, #-, )
Matthias WERREN (2nd Round, #-, 25y 261d)
Peter DOERNER (1st Round, #204, 19y 68d)
Ray WILSON (1st Round, #-, 34y 67d)
Roland Garros 1970
Andrew PATTISON (1st Round, #24, 21y 96d)
Jean-Francois CAUJOLLE (1st Round, #71, 18y 35d)
Karl MEILER (1st Round, #20, 21y 6d)
Anatoli VOLKOV (1st Round, #-, 22y 59d)
Antonio MUNOZ (1st Round, #74, 19y 66d)
Bob RHEINBERGER (1st Round, #162, 24y 170d) [LL]
Franco BARTONI (1st Round, #-, 21y 214d)
Francois MATHEU (1st Round, #-, 26y 102d)
Frantisek PALA (3rd Round, #102, 26y 40d)
Geza VARGA (1st Round, #228, 25y 173d)
Greg PERKINS (1st Round, #265, ) [LL]
Hakan ZAHR (1st Round, #-, 22y 20d)
Hans KARY (2nd Round, #54, 21y 72d)
Harald ELSCHENBROICH (1st Round, #69, 28y 323d)
Jean LOVERA (1st Round, #-, 19y 19d)
Jean-Paul MEYER (2nd Round, #265, 20y 125d)
Jun KUKI (1st Round, #74, 24y 130d)
Keith DIEPRAAM (1st Round, #-, 27y 239d)
Robert MACHAN (1st Round, #102, 21y 200d)
Szabolcs BARANYI (3rd Round, #94, 26y 97d)
Teimuraz KAKULIA (2nd Round, #91, 23y 11d)
Wanaro N'GODRELLA (1st Round, #71, 20y 199d)
William FREER (2nd Round, #237, 19y 58d)
Wimbledon 1970
Byron BERTRAM (3rd Round, #51, 17y 240d)
Guillermo VILAS (1st Round, #2, 17y 313d)
Hank IRVINE (1st Round, #-, 26y 301d)
Jack SAUL (2nd Round, #-, 26y 300d)
Roger DOWDESWELL (1st Round, #64, 26y 133d)
Stephen WARBOYS (1st Round, #73, 16y 244d)
US Open 1970
Brian GOTTFRIED (1st Round, #3, 18y 223d)
Jimmy CONNORS (1st Round, #1, 17y 4d)
Sandy MAYER (1st Round, #7, 18y 154d)
Steve KRULEVITZ (1st Round, #74, 19y 100d)
Atet WIJONO (1st Round, #-, 19y 180d)
Bob ALLOO (1st Round, #-, 21y 123d)
Frank FROEHLING (2nd Round, #67, 28y 113d)
King VAN NOSTRAND (1st Round, #-, 36y 99d)
Mike MACHETTE (1st Round, #92, 19y 223d)
Mohammed-Arif ELAHI (2nd Round, #-, )
Richard WALTHALL (1st Round, #238, 20y 203d)
Tito VAZQUEZ (4th Round, #85, 21y 249d)
Turner HOWARD (1st Round, #-, 23y 46d)
William BROWN (2nd Round, #86, 25y 237d)