World No. 1 Williams disposed of Spain's Lourdes Dominguez Lino 6-2, 7-5, claiming her 13th straight win. Russia's Sharapova made quick work of American qualifier Christina McHale 6-1, 6-2.
Elsewhere at the Magic Box Tuesday, Svetlana Kuznetsova upended 11th-seeded fellow Russian Nadia Petrova, 7-6 (7-2), 4-6, 6-4, and No. 14 Marion Bartoli of France overcame Spanish qualifier Maria-Teresa Torro-Flor 6-4, 2-6, 6-4.
Also Tuesday, Germany's Sabine Lisicki needed a pair of tiebreakers to get past 15th-seeded Slovakian Dominika Cibulkova 7-6 (7-4), 7-6 (7-3), and No. 16 Ana Ivanovic of Serbia bested South African qualifier Chanelle Scheepers 6-2, 6-2.
Kazakhstan's Yaroslava Shvedova and Spaniard Anabel Medina Garrigues also posted wins Tuesday.