Progression
The I–bVII–IV–I in G major
I–bVII–IV–I in G major plays G, F and C — I, bVII and IV — across 4 chords. The mixolydian rock cadence — a flattened seventh in place of the leading tone — behind riffs from classic rock to jam-band vamps.
The chords, in order
1GI
2FbVII
3CIV
4GI