Boulevard Transit Co. - in 1921 introduced service Milwaukee-Racine, Milwaukee-Waukesha; in 1922 introduced service Milwaukee-Hartford, Milwaukee-Fond Du Lac, Milwaukee-Madison; in 1922 sold to WMBL.
Lakeshore Transportation Co. - in 1921 introduced service Racine-Kenosha, Racine-Burlington; in 1923 sold to WMBL.
Eastern Wisconsin Transportation Co. - in 1922 introduced service Milwaukee-Fond Du Lac; in 1922 route sold to WMBL.
Milwaukee-Western Auto Service - in 1922 introduced service Milwaukee-Oconomowoc; in 1922 sold to WMBL.
Highway Transit Co. - in 1922 introduced service Milwaukee-Watertown; in 1922 bankrupt.
Turnpike Transit Co. - in 1922 introduced service Milwaukee-Oconomowoc; in 1923 ceased operations.
Walter's Bus Line - in 1923 introduced luxury sedan service Milwaukee-Waukesha; in 1925 sold to WMBL.
Pickwick Stage Line - in 1923 briefly operated luxury sedan service Milwaukee-Oconomowoc.
Packard Deluxe Line - in 1923 introduced luxury sedan service Milwaukee-Fond Du Lac, Milwaukee-Hartford; in 1924 ceased operations.
Gray Motor Stage Line - in 1923 introduced service Janesville-Watertown-Beaver Dam; in 1926 sold to WMBL.
Knilan Bus Co. - in 1926 introduced luxury sedan service Milwaukee-Fort Atkinson; in 1927 ceased operations; WMBL also ceased competing service.
Menomonee Falls Transportation Co. - operated Milwaukee-Menomonee Falls; in 1927 sold to WMBL.
American Coach Lines - in 1926 introduced service Milwaukee-Green Bay; in 1927 introduced service Milwaukee-Wauwatosa, Milwaukee-North Milwaukee; in 1927 sold to WMBL.