| Game |
| Result | Moves |
Year |
Event/Locale | Opening |
| 1. G Schmidt vs G P Gruen |
| 0-1 | 34 |
1981 |
NRW-ch | E18 Queen's Indian, Old Main line, 7.Nc3 |
| 2. A Weiermann vs G P Gruen |
| 0-1 | 49 |
1981 |
NRW-ch | A00 Uncommon Opening |
| 3. G P Gruen vs Schmittdiel |
| 1-0 | 46 |
1981 |
NRW-ch | E18 Queen's Indian, Old Main line, 7.Nc3 |
| 4. U Markmann vs G P Gruen |
| 1-0 | 10 |
1981 |
NRW-ch | E18 Queen's Indian, Old Main line, 7.Nc3 |
| 5. G P Gruen vs C Panzeri |
| 1-0 | 40 |
1981 |
WchT U26 | E11 Bogo-Indian Defense |
| 6. R Lau vs G P Gruen |
| 0-1 | 30 |
1981 |
NRW-ch | E12 Queen's Indian |
| 7. G P Gruen vs S Ingenerf |
| 0-1 | 61 |
1981 |
NRW-ch | E69 King's Indian, Fianchetto, Classical Main line |
| 8. W Beckemeyer vs G P Gruen |
| 1-0 | 40 |
1981 |
NRW-ch | B64 Sicilian, Richter-Rauzer Attack |
| 9. W Groenegress vs G P Gruen |
| ½-½ | 50 |
1981 |
NRW-ch | B22 Sicilian, Alapin |
| 10. G P Gruen vs E Vladimirov |
| 0-1 | 57 |
1981 |
WchT U26 | E15 Queen's Indian |
| 11. G P Gruen vs M Mudersbach |
| 1-0 | 60 |
1981 |
NRW-ch | D31 Queen's Gambit Declined |
| 12. Hort vs G P Gruen |
| 1-0 | 39 |
1983 |
BL 8283 ;BL | A00 Uncommon Opening |
| 13. G P Gruen vs Spassky |
| ½-½ | 22 |
1983 |
BL | E91 King's Indian |
| 14. G P Gruen vs Hebden |
| 1-0 | 56 |
1983 |
ChEt | E92 King's Indian |
| 15. G P Gruen vs Sosonko |
| ½-½ | 17 |
1983 |
BL 8283 ;BL | D38 Queen's Gambit Declined, Ragozin Variation |
| 16. Romanishin vs G P Gruen |
| 1-0 | 38 |
1983 |
Plovdiv ETC | E17 Queen's Indian |
| 17. G P Gruen vs Chandler |
| ½-½ | 51 |
1983 |
Bundesliga 1982/83 | D34 Queen's Gambit Declined, Tarrasch |
| 18. G P Gruen vs Tringov |
| 1-0 | 52 |
1984 |
Hamburg op | E68 King's Indian, Fianchetto, Classical Variation, 8.e4 |
| 19. A Pyhala vs G P Gruen |
| 1-0 | 40 |
1985 |
Pohja | C51 Evans Gambit |
| 20. G P Gruen vs D King |
| 0-1 | 35 |
1987 |
BL2-W 8788 | A90 Dutch |
| 21. H Westerinen vs G P Gruen |
| 0-1 | 32 |
1987 |
BRD-BL Bamberg/Braun | C31 King's Gambit Declined, Falkbeer Counter Gambit |
| 22. G P Gruen vs Nunn |
| ½-½ | 28 |
1987 |
BL 8687 ;BL | E60 King's Indian Defense |
| 23. Hort vs G P Gruen |
| 1-0 | 47 |
1987 |
BL 8687 ;BL | A22 English |
| 24. Christiansen vs G P Gruen |
| 1-0 | 39 |
1988 |
Bad Mergentheim GER op | A46 Queen's Pawn Game |
| 25. H Metz vs G P Gruen |
| ½-½ | 18 |
1988 |
Schoneck | C36 King's Gambit Accepted, Abbazia Defense |