| Game |
| Result | Moves |
Year |
Event/Locale | Opening |
| 26. A S Segal vs H MacGrillen |
| 1-0 | 47 |
1969 |
WchT U26 qual-A | D32 Queen's Gambit Declined, Tarrasch |
| 27. M Benoit vs H MacGrillen |
| 0-1 | 53 |
1969 |
WchT U26 fin-C 16th | C26 Vienna |
| 28. H MacGrillen vs V Tukmakov |
| 0-1 | 32 |
1969 |
WchT U26 qual-A | A27 English, Three Knights System |
| 29. R Meertens vs H MacGrillen |
| 0-1 | 39 |
1969 |
WchT U26 fin-C 16th | E92 King's Indian |
| 30. H MacGrillen vs G Sigurjonsson |
| ½-½ | 47 |
1969 |
WchT U26 qual-A | E92 King's Indian |
| 31. H MacGrillen vs C W Pritchett |
| ½-½ | 41 |
1969 |
WchT U26 fin-C 16th | E56 Nimzo-Indian, 4.e3, Main line with 7...Nc6 |
| 32. N Kazilaris vs H MacGrillen |
| ½-½ | 41 |
1969 |
WchT U26 qual-A | D16 Queen's Gambit Declined Slav |
| 33. H MacGrillen vs K Teboudi |
| ½-½ | 47 |
1969 |
WchT U26 fin-C 16th | A27 English, Three Knights System |
| 34. H MacGrillen vs P G Henry |
| ½-½ | 59 |
1971 |
Cork op | D37 Queen's Gambit Declined |
| 35. J Moles vs H MacGrillen |
| 1-0 | 19 |
1971 |
Cork op | B47 Sicilian, Taimanov (Bastrikov) Variation |
| 36. A Coldrick vs H MacGrillen |
| ½-½ | 27 |
1971 |
Cork op | B93 Sicilian, Najdorf, 6.f4 |
| 37. R Byrne vs H MacGrillen |
 | 0-1 | 36 |
1971 |
Cork op | E92 King's Indian |
| 38. H MacGrillen vs G McCurdy |
| 1-0 | 49 |
1971 |
Cork op | A73 Benoni, Classical, 9.O-O |
| 39. H MacGrillen vs F Trois |
| ½-½ | 10 |
1972 |
Skopje ol (Men) final-C | A53 Old Indian |
| 40. H MacGrillen vs J Durao |
| 0-1 | 38 |
1972 |
Skopje ol (Men) final-C | E74 King's Indian, Averbakh, 6...c5 |
| 41. H MacGrillen vs T Hay |
| ½-½ | 58 |
1972 |
Skopje ol (Men) fin-C | E73 King's Indian |
| 42. J Durao vs H MacGrillen |
| 1-0 | 18 |
1972 |
Skopje ol (Men) prelim | B06 Robatsch |
| 43. H MacGrillen vs G Bonner |
| 0-1 | 58 |
1972 |
Skopje ol (Men) final-C | B22 Sicilian, Alapin |
| 44. H MacGrillen vs E Gonzales |
| ½-½ | 28 |
1972 |
Skopje ol (Men) final-C | D25 Queen's Gambit Accepted |
| 45. H MacGrillen vs R Chavez Chavez |
| 1-0 | 39 |
1972 |
Skopje ol (Men) fin-C | E42 Nimzo-Indian, 4.e3 c5, 5.Ne2 (Rubinstein) |
| 46. H MacGrillen vs S Krstic |
| ½-½ | 21 |
1972 |
Skopje ol (Men) prelim | E92 King's Indian |
| 47. H MacGrillen vs E Martinez |
| ½-½ | 15 |
1972 |
Skopje ol (Men) final-C | D10 Queen's Gambit Declined Slav |
| 48. H MacGrillen vs M Yeo |
| 0-1 | 52 |
1972 |
Islington op | C73 Ruy Lopez, Modern Steinitz Defense |
| 49. S Hutchings vs H MacGrillen |
| ½-½ | 40 |
1972 |
Skopje ol (Men) final-C | A25 English |
| 50. H MacGrillen vs M C Lopez |
| ½-½ | 37 |
1972 |
Skopje ol (Men) fin-C | A56 Benoni Defense |