Model comparison
GPT-OSS 20B vs Grok 4 Fast (Reasoning)
Head-to-head evidence from 11 shared benchmark results across 5 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.
Public leaderboard positions: GPT-OSS 20B #159 (Supported); Grok 4 Fast (Reasoning) #76 (Supported). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. GPT-OSS 20B and Grok 4 Fast (Reasoning) share 11 comparable benchmark results. 0 of 8 categories are comparable. 7 results are unique to GPT-OSS 20B; 2 to Grok 4 Fast (Reasoning).
Updated July 23, 2026- Shared results
- 11
- GPT-OSS 20B only
- 7
- Grok 4 Fast (Reasoning) only
- 2
- Comparable categories
- 0 / 8
Benchmark data for GPT-OSS 20B and Grok 4 Fast (Reasoning) is coming soon on BenchLM.
Confidence note. This is a partial-evidence comparison with 11 shared benchmark results across 5 evidence categories; 0 of 8 categories currently have scoreable aggregates for both models. Treat the verdict as directional until coverage is more balanced.
Why this result
BenchLM has partial data for these models, but not enough overlapping benchmark coverage to produce a fair score-level comparison yet.
Grok 4 Fast (Reasoning) has the larger context window at 2M, compared with 128K for GPT-OSS 20B.
Category breakdown
Exact category averages are shown below. Not measured means BenchLM does not have enough sourced public coverage for that model and category.
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | GPT-OSS 20B | Grok 4 Fast (Reasoning) | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | GPT-OSS 20B$0 input / $0 output | Grok 4 Fast (Reasoning)Not available | A complete price comparison is not available. |
| Generation speedtokens per second | GPT-OSS 20B313 tok/s | Grok 4 Fast (Reasoning)Not available | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | GPT-OSS 20B0.65 s | Grok 4 Fast (Reasoning)Not available | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | GPT-OSS 20B128K | Grok 4 Fast (Reasoning)2M | Grok 4 Fast (Reasoning) lists the larger context window. |
Benchmark Deep Dive
Agentic5 benchmarks
Coding4 benchmarks
Reasoning2 benchmarks
Knowledge6 benchmarks
| Benchmark | GPT-OSS 20B | Grok 4 Fast (Reasoning) | Result |
|---|---|---|---|
| Artificial Analysis Intelligence IndexSource | 14.9% | 27.4% | Grok 4 Fast (Reasoning) leads |
| AA-GPQA DiamondSource | 68.8% | 84.7% | Grok 4 Fast (Reasoning) leads |
| AA-HLESource | 9.8% | 17.0% | Grok 4 Fast (Reasoning) leads |
| AA-Omniscience IndexSource | -63.9% | -28.4% | Grok 4 Fast (Reasoning) leads |
| AA-Omniscience AccuracySource | 15.5% | 22.6% | Grok 4 Fast (Reasoning) leads |
| AA-Omniscience Hallucination RateSource | 94.1% | 66.0% | Grok 4 Fast (Reasoning) leads |
Multimodal2 benchmarks
Inst. Following1 benchmarks
| Benchmark | GPT-OSS 20B | Grok 4 Fast (Reasoning) | Result |
|---|---|---|---|
| AA-IFBenchSource | 65.1% | 50.5% | GPT-OSS 20B leads |
Frequently Asked Questions (3)
Can I compare GPT-OSS 20B and Grok 4 Fast (Reasoning) on BenchLM yet?
Not fully yet. BenchLM is tracking both models, but the sourced benchmark breakdown for this comparison is still coming soon.
Why does this comparison show “coming soon”?
BenchLM only shows category winners and benchmark-level calls when we have sourced results that can be compared fairly. For these models, the public benchmark coverage is not complete enough yet.
What data is available for GPT-OSS 20B and Grok 4 Fast (Reasoning) today?
GPT-OSS 20B: $0.00 input / $0.00 output per 1M tokens Both model pages still include creator, context window, reasoning mode, and other metadata while benchmark coverage fills in.
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