Halep dispatched Agnes Bukta 6-1, 6-1 in 50 minutes. She lost nine points in seven games serving and finished with five breaks. In addition to winning three-quarters of the points on serve, Halep took 60 percent of the points when Bukta served.
Halep won a pair of tournaments leading up to Wimbledon and has won 13 of her last 14 matches.
No. 4-seeded Annika Beck advanced in straight sets Wednesday but fifth-seeded Johanna Larsson and seventh-seeded Maria-Teresa Torro-Flor both lost in three.
Beck defeated Lucie Hradecka 6-3, 6-3, recording five breaks over Hradecka nine games serving.
Yvonne Meusburger rallied for a 3-6, 6-4, 6-4 win over Larson. Each player had six breaks but Meusburger had two in each set while four of Larson's came in the opening set.
Timea Babos edged Torro-Flor 1-6, 6-4, 7-6 (7-4). Babos lost serve twice in the first set but won about two-thirds of the points on serve the rest of the way.
Halep and Babos are to play in Friday's quarterfinals with Beck and Meusburger matched against each other.