Left back Alaba scored either side of a sensational Bastian Schweinsteiger free kick with Mario Gomez, starting ahead of top scorer Mario Mandzukic, drilling in the fourth as Bayern made it four straight wins this year without conceding a goal.
In another impressive display of fluid, attacking football, Bayern outplayed Schalke, launching an avalanche of pressure from the start and missing several other clear chances as they chase their first title after two failed campaigns.
Bayern move on to 54 points with their 17th win in 21 league games while fellow Champions League competitors Schalke, badly missing a string of injured players and having notched only one win in their last 10 games, dropped to ninth.
