I have a 5.25" floppy in storage that is DOS 2.11 and it has GW-Basic on it. I think DOS 2.11 was the first to come with GW-Basic.
When purchasing a retail copy of MS-DOS, people will have trouble getting a version earlier than 3.20. Microsoft did not offer a generic version of MS-DOS until v3.20 in 1986 and before then, all variants of the OS were OEM ones. Depending on the OEM, BASIC was distributed as either BASICA.EXE or GWBASIC.EXE. I was looking at the paper manual I have for GW-Basic which says "This version of GW-BASIC requires MS-DOS version 3.2 or later."
The initial version of GW-BASIC was the one included with Compaq DOS 1.13 (released with the Compaq Portable in 1983) and was analogous to IBM BASICA 1.10. It used the CP/M-derived file control blocks for disk access and did not support subdirectories. Later versions added this feature and improved graphics and other capabilities.
GW-BASIC 3.20 (1986) added EGA graphics support (no version of BASICA or GWBASIC had VGA support) and was in effect the last new version released before it was superseded by QBASIC.