Use the output from subplot to store the axes. Then set the XLim and YLim of the axes.
figure
ax = zeros(3,1);
ax(1) = subplot(3,1,1);
bar(1:10,3*rand(1,10))
ax(2) = subplot(3,1,2);
bar(1:20,2*rand(1,20))
ax(3) = subplot(3,1,3);
bar(1:30,rand(1,30))
set(ax,'XLim',[-5 35],'YLim',[-2 5],'XTickMode','auto','YTickMode','auto');
