o1 vs GPT-OSS 20B

Side-by-side benchmark comparison across knowledge, coding, math, and reasoning.

o1 is clearly ahead on the aggregate, 51 to 34. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.

o1's sharpest advantage is in knowledge, where it averages 83.8 against 28.2. The single biggest benchmark swing on the page is MMLU, 91.8 to 31.

o1 is the reasoning model in the pair, while GPT-OSS 20B is not. That usually helps on harder chain-of-thought-heavy tests, but it can also mean more latency and more token spend in real use. o1 gives you the larger context window at 200K, compared with 128K for GPT-OSS 20B.

Quick Verdict

Pick o1 if you want the stronger benchmark profile. GPT-OSS 20B only becomes the better choice if you would rather avoid the extra latency and token burn of a reasoning model.

Knowledge

o1

o1

83.8

GPT-OSS 20B

28.2

91.8
MMLU
31
75.7
GPQA
30
-
SuperGPQA
28
-
OpenBookQA
26
-
MMLU-Pro
53
-
HLE
1

Coding

o1

o1

41

GPT-OSS 20B

16

41
SWE-bench Verified
14
-
HumanEval
23
-
LiveCodeBench
11

Mathematics

o1

o1

74.3

GPT-OSS 20B

33.6

74.3
AIME 2024
33
-
AIME 2023
31
-
AIME 2025
32
-
HMMT Feb 2023
27
-
HMMT Feb 2024
29
-
HMMT Feb 2025
28
-
BRUMO 2025
30
-
MATH-500
59

Reasoning

GPT-OSS 20B
-
SimpleQA
29
-
MuSR
27
-
BBH
62

Instruction Following

o1

o1

92.2

GPT-OSS 20B

67

92.2
IFEval
67

Multilingual

GPT-OSS 20B
-
MGSM
61

Frequently Asked Questions

Which is better, o1 or GPT-OSS 20B?

o1 is ahead overall, 51 to 34. The biggest single separator in this matchup is MMLU, where the scores are 91.8 and 31.

Which is better for knowledge tasks, o1 or GPT-OSS 20B?

o1 has the edge for knowledge tasks in this comparison, averaging 83.8 versus 28.2. Inside this category, MMLU is the benchmark that creates the most daylight between them.

Which is better for coding, o1 or GPT-OSS 20B?

o1 has the edge for coding in this comparison, averaging 41 versus 16. Inside this category, SWE-bench Verified is the benchmark that creates the most daylight between them.

Which is better for math, o1 or GPT-OSS 20B?

o1 has the edge for math in this comparison, averaging 74.3 versus 33.6. Inside this category, AIME 2024 is the benchmark that creates the most daylight between them.

Which is better for instruction following, o1 or GPT-OSS 20B?

o1 has the edge for instruction following in this comparison, averaging 92.2 versus 67. Inside this category, IFEval is the benchmark that creates the most daylight between them.

Last updated: March 9, 2026

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