Lawless began the season as the Minor League roving infield instructor. He has managed at Class A Lexington (2009), Advanced Class A Lancaster (2010) and Double-A Corpus Christi (2011).
"Tom has managed in our system in the past, most recently with our Corpus Christi affiliate last season," said Astros director of player development Fred Nelson. "This move allows us to send an experienced manager to Oklahoma City, while keeping the rest of our field staffs intact."
Before becoming a manager, Lawless serves as an infield instructor for the Orioles from 2006-08. He played in eight Major League seasons with four different teams. His playing career ended in 1990.
Lawless will be with the team before tomorrow's game at Round Rock.