Bertrand, a 10th-round pick of the San Francisco Giants in the 2022 MLB Draft, struck out four hitters for the Squirrels (11-9), who have taken four of five so far this week from the Baysox (10-10).
Bertrand is now 3-3 with a 3.78 ERA and 1.33 WHIP in 15 career starts at the Double-A level.
Richmond, on Friday night, had taken a combined no-hitter into the ninth in a 4-2 win over the Baysox, the Double-A affiliate of the Baltimore Orioles.
On Saturday, Bowie broke up the perfect game with a walk in the top of the eighth by Frederick Bencosme and picked up its first hit with a single by TT Bowens.
After Bowie loaded the bases with one out in the eighth, Wil Jensen struck out the next five batters to finish the game.
The offense came from Adrián Sugastey, who broke a scoreless tie in the fifth with a three-run homer, his first at Double-A.
Two batters later, Dilan Rosario hit his first Double-A homer, a solo shot, to extend the lead to 4-0.